Regioselectivity in the photochemical ring contraction of 4-diazopyrazolidine-3,5-diones to give aza-beta;-lactams

摘要

J. CHEM. SOC. PERKIN TRANS. I 1987 Reg ioselect ivity in the Photochemical Ring Contraction of 4-Diazopyrazolidine-3,5-diones to give Aza-p-lactams Geoffrey Lawton Roche Products Ltd., P.O. Box 8 Welwyn Garden City, Hertfordshire AL7 3AY Christopher J. Moody,' Christopher J. Pearson, and David J. Williams Department of Chemistry, Imperial College of Science and Technology, London S W7 2A Y Irradiation of 4-diazopyrazolidine-3,5-diones (I 5) in the presence of alcohols or water gave mixtures of the isomeric 1,2-diazetidinones (I6) and (17), formed by competing photochemical Wolff rearrangement of the two nitrogen groups, followed by reaction of the resulting ketenes with the nucleophile. Some regioselectivity is observed in the ring contraction process, and the relative order of migration of nitrogen groups is NPh NCHPh, -NCH,Ph -NMe NCH,CO,Et.The structures of the 1,2-diazetidinones (17c) and (24) were confirmed by X-ray crystallography, and a crystal structure of the diazo compound (15g) was also obtained. Possible reasons for the regioselectivity in the ring contraction are discussed. In the preceding paper we reported the details of a new route chloride followed by base mediated cyclisation, hydrolysis and to 1,2-diazetidinones, aza analogues of p-lactams, based on the decarboxylation gave the pyrazolidine-3,5-diones (4a,c) photochemical ring contraction of symmetrically substituted 4-(Scheme 2). diazopyrazolidine-3,5-dionesin the presence of a nucleophile (Scheme l).' The success of this reaction demonstrated that E10,C NR EIOZCNR -idespite the participation of the nitrogen lone pair in amide I I NHCHZPhresonance, the nitrogen atom would migrate to the electron NwPh deficient centre to effect the desired ring contraction.In general N-C bonds show a marked reluctance to migrate in the photo- chemical Wolff rearrangement,, and only a few examples are known.3 ii1 EtOZCNR ... IIll NCH2Ph EIOzC~NCH~PhCY0 0 Scheme 1. R = PhCH,, Pr,or RR = (CH,),; Nu = EtO, Bu'O, Et,N or HO (41 (3) a, R=Me; c, R =Ph We have now investigated this reaction in more detail with a Scheme 2. Reagents: i, H,, Pd-C, EtOH; ii, EtO,CCH,COCI, Et,N,view to determining the electronic and steric requirements for C,H,; iii, NaOEt, EtOH; iv, H,O, MeCN, refluxnitrogen atoms to migrate in the Wolff rearrangement, and to extending the range of aza-p-lactams available by this route.Our results on the photochemical ring contraction of un-Although the sodium ethoxide cyclisation worked well for the symmetrically substituted 4-diazopyrazolidine-3,5-dionesare simple alkyl and aryl substituted pyrazolidinediones, it seemed reported in detail herein4 likely that problems would arise when other functional groups such as esters were present, and therefore an alternative route to pyrazolidinediones was developed (Scheme 3).Results and Discussion Condensation of t-butyl carbazate with aldehydes or ketones Preparation of 4-Diazopyrazolidine-3,5-diones.-Eight mono-gave the expected t-butyloxycarbonylhydrazones (5), which and bi-cyclic unsymmetrical 4-diazopyrazolidine-3,5-diones were readily alkylated to give the hydrazones (6).Reduction (15) were prepared, containing a range of substituents. The of the C=N bond by catalytic hydrogenation or by sodium choice of substituents bearing carboxylate groups is influenced cyanoborohydride gave the hydrazines (7),which were acylated by the fact that any potential p-lactam analogue would almost with ethoxycarbonylacetyl chloride, and then cyclised by treat- certainly require such a substituent. The 2-methyl- and 2-ment with trifluoroacetic acid (TFA). The pyrazolidinediones phenyl-1-benzylpyrazolidine-3,5-diones(4a,c) were prepared by (4b), (a),and (40 were prepared by this route. The inter- a similar route to that already used for the symmetrical 1,2-mediate hydrazine (7c) was obtained from the known Bu'0,-dialkyl derivatives.Thus the ethyl benzylidenecarbazates (la), CNHNHCH,CO,Et by acylation with benzyl chloroformate, prepared by methylation of ethyl benzylidenecarbazate itself, methylation, and removal of the benzyloxycarbonyl group by and (lc), prepared by acylation of benzaldehyde phenyl- hydrogen01 ysis. hydrazone, were hydrogenated to give the corresponding benzyl Although the ring contraction of bicyclic 4-diazopyrazolidine- derivatives (2). Acylation of (2) with ethoxycarbonylacetyl diones had already been found to be less satisfactory than in the 886 Bu'0,C NH BU O2CNHNHz Bu 0,C NR3 B ut I iii R2 (7) liv But 0,CNR3 - 0 Et0,CQ R' 0'J $!;R' R2 (4) (5)-(8) R1 R2 R3 b a Ph Ph Me d bPhH C HzCOZEt c H COtEt Me f d Ph CO2CHZPh Me Scheme 3.Reagents: i, R'R'CO, EtOH; ii, R3X, K,CO,, acetone; iii, H,, Pd-C, EtOH or NaBH3CN, THF, H'; iv, EtO,CCH,COCl, Et3N, C,H,; v, TFA, CH,CI,. Nofe.(7c) was prepared differently- see text. monocyclic series, ' an investigation into unsymmetrical bicyclic compounds was still considered worthwhile, and therefore the preparation of the precursor pyrazolidinediones (4g)and (4h) was undertaken. 0 0Q? p?C0,Bu' CO,But Fortunately the pyrazolopyridazine derivative (4g) was readily available from other work,6 and a similar route was used to prepare the five-membered ring analogue (4h)(Scheme 4).Cycloaddition of diazomethane to t-butyl acrylate gave the 4,5-dihydropyrazole (9)as the major product, together with some of the required azo compound (10). Since the rearrangement of (10)into (9)was sufficiently slow, immediate catalytic hydrogen- ation of the reaction mixture resulted in the reduction of (10) to the cyclic hydrazine (11). When the mixture of (9)and (11) was acylated with benzyl chloroformate, selective reaction of N-1 of (11) occurred to give, after chromatographic separation of the J. CHEM. SOC. PERKIN TRANS. I 1987 unwanted (9), the pyrazolidine (12) in 18 overall yield. Acylation of (12) with ethoxycarbonylacetyl chloride, followed by hydrogenolysis of the benzyloxycarbonyl group gave (14), which was cyclised to (4h)under basic conditions.*CO,But N +"'3 / 'c0,Bu' b0,Bu' (9) (10) 1ii .. . Ill -",? C0,Bu' (12) (11) 1. P h CH2 02CN (4h) CO, But 0 0 Scheme 4. Reugenfs: i, CH,N,, ether; ii, H,, Pd-C, EtOH; iii, PhCH,OCOCI; iv, chromatography; v, EtO,CCH,COCI, Et3N, Et,O; vi, NaOEt, EtOH, reflux The pyrazolidinediones (4)were converted into the corres- ponding 4-diazo derivatives (15) under standard conditions using tosyl azide as diazo-transfer reagent. Photochemical Ring Contraction Reactions.-The 4-diazo-pyrazolidine-3,5-diones (15) were irradiated in ether in the presence of a nucleophile such as methanol, ethanol, or water, to give mixtures of the diazetidinones (16) and (17). The results are summarised in Table 1.The ratio of the four-membered ring products was determined by integration of the appropriate signals in the 'H n.m.r. spectra of the mixtures. The assignment of signals corresponding to the diazetidinones (16) and (17) was confirmed by chromatographic separation of the regioisomers as their esters, obtained directly from photolysis in the presence of alcohols, or as the 4-unsubstituted compounds (18) and (19) obtained by decarboxylation * of the corresponding carboxylic acids (16) and (17) (Nu = HO). In general it was assumed that (16) (19) (18)J19) R' R2 R3 a Ph Ph Me b H Ph Ph C Ph CH,CO,Et d C0,Bu' -CH -(CH2I3- J. CHEM. SOC. PERKlN TRANS. I 1987 Table 1. Photochemical ring contraction of 4-diazopyrazolidine-3,5-diones(R = PhCH,, E = EtO,CCH,) Diazo compound Diaze ti- Diazeti- (15) dinone (16) dinone (17) 0 * N2 NU5NMeNRI N+NR 1 EtOH 30 1:1 HOH 33 1:1 0 EtOH 36 1:1 HOH 33 1:1 EtOH 72 1.7:l HOH 55 1.6:l NUkYRNEd Nz{YR NE MeOH 2.5:1 " HOH 47 2.8:l 0 MeOH 2:1" 0 HOH 0 EtOH 12 10:1 HOH 14 10:1 h 11 10:1 C0,Bu' -EtOH 0 OhN+ C02Bu* " Isomeric mixture could not be obtained pure; ratio from 'H n.m.r.Photolysis carried out in dry ether; see text. protons on a substituent attached to N-2 would resonate at the photolysis of (1) the N-phenyl substituent shows a slight lower field than if the same substituent were on N-1. preference to migrate over the N-benzyl group to give the 2-The initial results with respect to regioselectivity were benzyl-1 -phenyl-diazetidinone (16c) as the major product.The disappointing, N-methyl, N-benzyl, and N-benzhydryl groups structure of the minor product from the photolysis in the having similar migratory aptitudes and leading to 1 :1 mixtures presence of ethanol, ethyl 1-benzyl-2-phenyl-3-oxodiazetidine-of the regioisomeric diazetidinones (16) and (17). However, in 4-carboxylate (17c; Nu = EtO) was confirmed by its indepen- J. CHEM. SOC. PERKIN TRANS. I 1987 dent synthesis,' and by a single crystal X-ray structure analysis (see below). Greater regioselectivity was observed in the photolysis of the diazo compound (15d). When methanol was used as a ketene trap, the n.m.r. spectrum of the crude photolysate was com- plicated by the presence of dimethyl malonate and the hydra- zone (20),formed by a competing fragmentation reaction,' although the methyl ester signals of the diazetidinones (la)and (17d) (Nu = MeO) were tentatively assigned.Chromatography failed to remove the hydrazone (20)and separate the isomers. However, irradiation in the presence of water gave the corre- sponding acids (la)and (17d) (Nu = HO) uncontaminated with (20), which were decarboxylated, and the resulting C-4 unsubstituted diazetidinones (18) and (19) separated by chromatography, and the ratio of the isolated yields determined. NHR' I (20) R' = CH,Ph, R2 = C02E1, R3= H (21) R'= Me, I?' = CO2E1, R3 = H (22) R'= Me, R2 = Ph, R3 = C02CH2Ph When the benzyl group was replaced by a methyl as in diazo compound (15e), the major products from photolysis in the presence of methanol were dimethyl malonate and the hydra- zone (21).Chromatography removed the dimethyl malonate and gave an inseparable mixture of the hydrazone (21)and the diazetidinones (16; Nu = MeO) and (17e; Nu = MeO).By careful inspection of the 'H n.m.r. spectrum of this mixture it was possible to determine the ratio of (16; Nu = MeO) to (17e; Nu = MeO) as 2: 1, although it was not possible to separate the pure diazetidinones. Irradiation of the diazo compound (150 gave no detectable aza-P-lactams, and even the hydrazone (22)was not formed by the alternative fragmentation pathway. This result was particu- larly disappointing in that the aza-P-lactam (160 would have been a useful model for the synthesis of an aza-nocardicin analogue.The reluctance of an N-alkyl group bearing an electron with- drawing ester substituent to migrate, observed in the photolysis of (15d) and (15e), is more marked in the ring contraction of the bicyclic diazo compound (15g), where the Wolff rearrangement was highly regio- and stereo-selective and only one of the possible regioisomeric diazetidinones was isolated. However, the yields of four-membered ring products were low since frag- mentation of the intermediate to carbon suboxide and the tetra- hydropyridazine (23)(formed by isomerisation of the initially formed 3,4,5,6-tetrahydro isomer) competes very effectively with ring contraction.When the photolysis of (15g) was carried out in the presence of ethanol, diethyl malonate (46) and the pyridazine (23)(47) were isolated. The pyridazine (23)is itself sufficiently nucleophilic to intercept the ketene intermediate involved in the ring contraction, so that when (15g) was irradiated in dry ether in the absence of added nucleophiles, the only four-membered ring product was (24).The carboxylic acid (16g; Nu = HO) is decarboxylated in poor yield to give aza- P-lactam (la).Presumably the additional strain associated with the 6-4 bicyclic system makes the decarboxylation less fav ou ra ble. The structure of the bicyclic aza-f3-lactam (16g; Nu = EtO) was assigned on the basis of n.0.e. difference experiments which 0 "Q CO2BU' (231 (21) showed that the proton adjacent to the t-butyl ester group was not close to 1-H, but that 1-H was close to the axial proton at C-7.The regiochemistry of the ring contraction process was further confirmed by an X-ray crystallographic analysis of the 1,2-diazetidinone (24)(see below). In an attempt to prepare the more highly strained bicyclic aza-P-lactam (16h), the diazo compound (15h) was irradiated in ether-ethanol. However, no four-membered ring products were formed as evidenced by the lack of a high frequency carbonyl stretch in the i.r. spectrum of the crude product. Thus the photochemical ring contraction of unsymmetrical 4-diazopyrazolidine-3,5-dionesexhibits some degree of regio- selectivity, the relative migratory aptitudes of nitrogen groups following the order: NPh NCHPh, -NCH,Ph -NMe NCH,CO,Et.The Wolff rearrangement of unsymmetrical 2- diazo- 1,3-dicarbonyl compounds has been investigated, and the relative migratory aptitude of hydrogen, alkyl, aryl, and heteroatom groups studied.* In general the results show that in R'COCN,COR2 an electron poor R'-CO bond favours migration of the group R'. If this group, R', possesses a lone pair of electrons capable of participating in resonance with the carbonyl, then the group R2 migrates in preference. Thus there are several examples of carbon us. heteroatom migration but very few examples in which both migrating groups are heteroatoms. The limited results available indicate that nitrogen migrates in preference to oxygen, but the present work provides the first indications of the relative migratory aptitudes of differently substituted nitrogen atoms in the Wolff rearrangement.In the series of monocyclic diazopyrazolidinediones, the results suggest that the nitrogen bearing the more electron donating substituent migrates preferentially in the Wolff re- arrangement.' Although it seems reasonable that the N-alkyl group bearing an electron-withdrawing ester substituent should be more reluctant to migrate to an electron-deficient centre, the very high selectivity observed in the ring contraction of the bicyclic diazo compound (15g) is puzzling, since on electronic grounds a similar ratio to that observed in the photolysis of (15d)was expected. One possible explanation for the increased selectivity in the bicyclic series was uncovered by a single crystal X-ray analysis of the diazo compound (15g) (Figures 1 and 2).The X-ray structure shows that the geometry of the two bridgehead nitrogens is different. The migrating nitrogen atom, N-9, is the more planar of the two, the sum of the angles about N being 353.6' (cJ 343.9' at N-4), and it is closer to the plane defined by C(l)-C(2)-C(3) than N-4 (Figure 2). Hence one possible explanation for the observed regioselectivity lies in the hybridisation of the migrating nitrogen, the more planar nitrogen migrating because its lone pair orbital is better aligned for overlap with, in the extreme, the vacant carbene p-orbital.The less planar nitrogen atom having more sp3 character has a lone pair less well disposed for such overlap. A similar explanation pertains to the preferred migration of the N-phenyl substituent, since a nitrogen bearing an N-aryl substituent would be expected to be more planar than a nitrogen bearing an alkyl group (see also discussion of inversion barriers below). J. CHEM. soc. PERKIN TRANS. I 1987 d C(17) Figure 1. The molecular structure of (1) giving the crystallographic numbering scheme Figure 2. Edge view of the 5-membered ring of (1) illustrating the relative deviations of N(4) and N(9) from the C( 1),C(2),C(3) plane, and the axial disposition of the t-butyl ester. Both N(4) and N(9) are pyramidal with deviations of 0.33 and 0.20 A respectively from the planes of their substituent atoms.N(4) Lies 0.11 A above the C( 1),C(2),C(3) plane and N(9) lies 0.05 A below X-Ray Crystal Structures of 1,2-Diazetidinones.-Although primarily undertaken to confirm their structures, the X-ray crystallographic analyses of the 1,2-diazetidinones (17c; Nu = EtO) (Figure 3) and (24) (Figures 4 and 5) are of interest in their own right, since no X-ray structures of 1,2-diazetidinones have been published to date. Nitrogen Inversion in 1,2-Diazetidinones.-One distinctive feature of C-4 unsubstituted 1,2-diazetidinones is the magnetic non-equivalence of the C-4 hydrogens caused by the N-1 atom which is capable of pyramidal inversion. A consequence of this is that these hydrogen atoms appear as AB systems in the 'H n.m.r.spectra. However, on warming the n.m.r. sample, these C(15)n U a71 Figure 3. The molecular structure of (17c) giving the crystallographic numbering scheme Figure 4. The molecular structure of (24) giving the crystallographic numbering scheme Figure 5. Partial side view of (24) illustrating the axial disposition of the t-but yl ester, and the respective planar and pyramidal geometries of N(3) and N(8). N(8) Lies 0.63 A from the plane of C(l),N(3),C(7) quartets coalesce, and hence the inversion barrier at N-1 can be determined.' * The inversion barriers for the diazetidinones described in this work, together with known values, are shown in Table 2.Table 2. N-1 Inversion barriers for 1,2-diazetidinones A0 (kcal Compd. R' RZ mol-' ) (18a) (19a) (1) Me CHPh, CH,Ph CH,Ph CHPh, Me Ph CH,Ph 19.5 19.1 19.7 19.0" CHPh, H 18.6 Ph Ph 13.3' Ref. 1. Ref. 11. 'Ref. 12. The results are consistent with other diazetidinones, although the diphenyl compound is reported to have a much lower Ha barrier as a result of the aryl substituent which flattens the pyramidal configuration at N-1. The effect of a similar flattening of nitrogen geometry by an aryl substituent in the regioselective formation of 1,2-diazetidinones has already been discussed. Experimental For general points see ref. 1. Ethyl 3-Benzylidene-2-methylcarbazate (la).-A vigorously stirred mixture of ethyl 3-benzylidenecarbazate (500 mg, 2.6 mmol), iodomethane (730 mg, 5.1 mmol), trimethylbenzyl- ammonium chloride (100 mg), aqueous sodium hydroxide (40; 2 ml) and benzene (30 ml) was heated under reflux for 9 h.After cooling, the layers were separated, and the organic layer was washed with water, dried, and evaporated to give the title compound (la) (470 mg, 88) as a yellow syrup (Found: C, 64.4; H, 6.9; N, 13.6. C, ,HI4N2O2 requires C, 64.1; H, 6.8; N, 13.6); v,,,.(neat) 1 700 and 1 605 cm-'; 6, (90 MHz; CDCI,) 1.35 (3 H, t), 3.37 (3 H, s),4.35 (2 H, q), 7.35 (3 H, m), and 7.72 (3 H, m); m/z 206 (M+). Ethyl 3-Benzyl-2-methylcarbazate (2a).-A solution of the carbazate (la) (950 mg) in ethanol (35 ml) was hydrogenated over 10 palladium-on-charcoal (50 mg) to give, after distill- ation, the title compound (2a) (820 mg, 8673, b.p.117-121 "C at 0.3 mmHg (Kugelrohr); 6,(90 MHz; CDCI,) 1.25 (3 H, t), 2.95 (3 H, s), 3.97 (2 H, s), 4.20 (2 H, q), 4.60 (1 H, br s, D,O exch.), and 7.35 (5 H, m); m/z 208 (M+),117, 106, and 91 (base). Ethyl 3-Benzyl-3-ethoxycarbonylacetyl-2-methylcarbazate (3a).-A solution of ethoxycarbonylacetyl chloride (3.8 g, 25 mmol) in benzene (25 ml) was added dropwise to a stirred, ice- cooled solution of the carbazate (2a) (5.2 g, 25 mmol) and triethylamine (2.5 g, 25 mmol) in benzene (100 ml). The mixture was stirred at room temperature for 12 h, filtered, and the filtrate evaporated to give the title compound (3a) (6.8 g, 84), 6, (60 MHz; CDCI,) 1.13 (3 H, t), 1.29 (3 H, t), 2.89 (3 H, s), 3.40 (2 H, AB, J 16 Hz); 3.8W.40 (4 H, m), 4.70 (2 H, AB, J 14 Hz), and 7.25 (5 H, s).1-Benzyl-2-methylpyrazolidine-3,5-dione(4a).-A mixture of the carbazate (3a) (6.5 g, 20 mmol) and sodium ethoxide from sodium (0.5 g, 22 mmol) in ethanol (1 10 ml) was heated under reflux for 5 h. The solvent was evaporated, and the residue dis- solved in water (150 ml), and extracted with ether. The aqueous layer was acidified and extracted with dichloromethane. The CH,CI, extracts were evaporated, the residue dissolved in a J. CHEM. SOC. PERKIN TRANS. I 1987 mixture of acetonitrile (100 ml) and water (10 ml), and the solution heated under reflux for 5 h. Evaporation followed by crystallisation of the residue from ethanol gave the title compound(4a) (4.0 g, 9773, m.p.104 "C (Found: C, 64.6; H, 5.9; N, 13.7. C,,H,,N202 requires C, 64.7; H, 5.9; N, 13.7); vmax.(Nujol) 1 740 and 1695 cm-'; 6, (60 MHz; CDCI,) 3.05 (3 H, s), 3.23 (2 H, s), 4.83 (2 H, s), and 7.28 (5 H, m); m/z 204 (M') and 91 (base). Ethyl 3-Benzylidene-2-phenylcarbazate (lc).-A solution of butyl-lithium in hexane (1.56~; 3.2 ml, 5 mmol) was added dropwise to a stirred solution of benzaldehyde phenylhydrazone (1.0 g, 5.1 mmol) in THF (8 ml) at -78 "C. The initial deep red colour was followed by the formation of a yellow precipitate. This suspension was stirred for 15 min, quenched with ethyl chloroformate (0.8 g, 8 mmol) and then warmed to room temperature. Aqueous work-up gave, after recrystallisation from cyclohexane, the title compound (lc) (1.1 g, 80), m.p.98.5 "C (Found: C, 71.6; H, 6.0 N, 10.4. C16H16N202 requires C, 71.6; H, 6.0; N, 10.4); v,,,,(Nujol) 1 730 cm-'; 6,(60 MHz; CDCI,) 1.32 (3 H, t), 4.30 (2 H, q), and 7.1-7.8 (1 1 H, m); m/z 268 (M+). Ethyl 3-Benzyl-2-phenylcarbazate(2c).-This was prepared by hydrogenation of the carbazate (lc) exactly as described for compound (2a) as a yellow oil (loo), v,,,.(neat) 3 310, 1 700, and 1 595 cm-I; 6, (60 MHz; CDCI,) 1.20 (3 H, t), 4.01 (2 H, d, J 6 Hz; gives a singlet with D,O), 4.20 (2 H, q), 4.99 (1 H, t, J 6 Hz, D20 exch.), and 6.90-7.70 (10 H, m); m/z 270 (M+). Ethyl 3-Benzyl-3-ethoxycarbonylacetyl-2-phenylcarbazate (*).-This was prepared by acylation of the carbazate (2c) exactly as described for compound (3a) as a pale yellow gum (83), v,,,,(neat) 1750, 1 680, and 1600 cm-'; 6, (60 MHz; CDCI,) 1.10 (3 H, t), 1.27 (3 H, t), 3.45 (2 H, AB, J 14 Hz), 4.17 (4 H, m), 4.40 (2 H, AB, J 14 Hz), and 7.05-7.60 (10 H, m).1-Benzy l-2-phenylpyrazo fidine- 3,5-dione (4c).-T his was pre- pared from the carbazate (3c) exactly as described for com- pound (4a) as a colourless solid (76), m.p. 109.5 "C(Found: C, 72.15; H, 5.3; N, 10.6. C16H,,N,O, requires C, 72.2; H, 5.3; N, 10.5); vmaX.(Nujol) 1 735, 1 710, and 1 595 cm-I; 6, (60 MHz; CDCI,) 3.30 (2 H, s), 4.70 (2 H, s), and 6.8-7.5 (10 H, m); m/z 266 (M+)and 91 (base). t-Butyl 3-Diphenylmethylenecarbazate (5a).-A mixture of benzophenone (6.88 g, 38 mmol), t-butyl carbazate (5.0 g, 38 mmol), acetic acid (1 ml) and ethanol (100 ml) was heated Binder reflux for 24 h.The solvent was evaporated and the residue crystallised from ethanol to give the title compound (5a) (10.5 g, 9479, m.p. 128 "C, v,,,.(Nujol) 1 740 cm-'; 6, (60 MHz; CDCI,) 1.50 (9 H, s), and 7.0-7.7 (1 1 H, m). t-Butyl 3-Diphenylmethylene-2-methylcarbazate (6a).-A stirred mixture of the carbazate (5a) (10.0 g, 33.8 mol), iodo- methane (6.0 g, 42 mmol), and potassium carbonate (10 g) in acetone (300 ml) was heated under reflux for 24 h. The mixture was filtered, and the filtrate evaporated to give the title com-pound(6a) (10.47 g, lo), m.p. 78 "C (Found: C, 73.5; H, 7.2; N, 9.0. C,,H,,N,O, requires C, 73.5; H, 7.1; N, 9.0); v,,,,(Nujol) 1 680 cm-'; 6, (60 MHz; CDCI,) 1.24 (9 H, s), 3.03 (3 H, s), and 7.15-7.70 (10 H, m); m/z 310 (M+),254, 237, 209 (base), 194, 180, 165, 139, 106, 104,91, and 77.t-Butyl 3-Diphenylmethyl-2-methylcarbazate(7a).-Bromo-cresol Green indicator (5 mg) was added to a stirred mixture of the carbazate (6a) (7.87 g, 25.4 mmol) and sodium cyano- borohydride (1.76 g, 26.2 mmol) in THF (60ml) and methanol J. CHEM. SOC. PERKIN TRANS. I 1987 (5ml) to give a dark blue solution. Dilute hydrochloric acid was then added at such a rate as to maintain a yellow colour of the solution. When the yellow colour persisted for 1 h without further addition of acid, the mixture was evaporated, and the residue partitioned between water and dichloromethane.The organic layer was separated, dried, and evaporated to give, after chromatography, the titlecompound(7a) (7.20g, 91),m.p.68"C (Found: C, 73.25;H, 7.8;N, 9.0.C,,H,,N,O, requires C, 73.05; H, 7.7;N, 9.0);v,,,.(Nujol) 3 275and 1 693cm-'; 6, (90MHz; CDCI,) 1.49 (9 H, s), 2.76 (3 H, s), 4.82 (1 H, br s, D,O exch.), 5.28(1 H, s), and 7.40 (10 H, m); m/z312 (M+),256, 239, 167 (base), 165,152, 104, 77,and 57. t-Bury1 3-Diphenylmethyl-3-ethoxycarbonylacetyl-2-methyl-carbazate @a).-The carbazate (7a) (5.62g, 18 mmol) was acylated with ethoxycarbonylacetyl chloride as described for compound (3a) to give the title compound(8a) (4.12g, 5473, m.p. 72-73 "C (Found: C, 67.5;H, 7.1;N, 6.7.C,,H,,N,O, requires C, 67.6;H, 7.1;N, 6.6);v,,,.(Nujol) 1 730,1 710,and 1 677cm-'; 6, (90MHz; CDCI,) 1.28 (9 H, s), 1.35 (3H, t), 2.98 (3H, br s), 3.44(2H, AB, J 15 Hz), 4.22(2H, q), 6.65and 6.75 (1 H, 2 br s), and 7.28(10 H, m); m/z426 (M+)354, 297, 167 (base), 152,115,and 57.1-Diphenylmethyl-2-methylpyrazolidine-3,5-dione(4b).-Tri-fluoroacetic acid (10ml) was added to a stirred solution of the carbazate (8a) (4.0g, 9.4mmol) in dichloromethane (70ml), and the resulting solution was stirred at room temperature for 48h. Evaporation of the solvent, and chromatography gave the title compound(4b) (2.30g, 87), m.p. 107.5"C (Found: C, 72.7;H, 5.7;N, 9.9.C,,H1,N,O2 requires C, 72.8;H, 5.75;N, 10.0); v,,,.(Nujol) 1730 and 1685 cm-'; 6, (60MHz; CDCI,) 2.95 (3H, s), 3.13 (2 H, s), 6.74(1 H, s), and 7.30(10 H, s); m/z 280 (M'), 167 (base), and 152.t-Bury1 3-Benzylidenecarbazate (Sb).-This was prepared by the literature method, l4 m.p. 184-188 "C (lit., 185-187 "C). t-Butyl 3-Benzylidene-2-(ethoxycarbonylmethyl)carbazate (6b).-Alkylation of the carbazate (5b) (5.0 g, 23 mmol) with ethyl bromoacetate (4.2g, 27 mmol) under the conditions described for compound (6a) gave the title compound(6b) (5.15 g, 7473,m.p. 79"C (from ethyl acetate-light petroleum) (Found: C, 62.9;H, 7.3;N, 9.1.C ,H2,N204 requires C, 62.7;H, 7.2;N, 9.1); v,,,.(Nujol) 1 743,1 695,and 1 610 cm-'; 6, (60MHz; CDCI,) 1.20 (3H, t), 1.53 (9H, s), 4.11 (2H, q), 4.50 (2H, s), 7.21 (3 H, m), 7.54 (2 H, m), and 7.85(1 H, s); m/z306 (M'), 206,133,88 (base), and 57.t-Butyl3-Benzyl-2-(ethoxycarbonylmethyl)carbazate(7b).-A solution of the carbazate (6b) (4.0g) in ethanol (100ml) was hydrogenated over 10 palladium-charcoal (0.3g). The catalyst was filtered off, and the filtrate evaporated to give the title compound (7b) (3.83g, 95) as a pale yellow oil, v,,,.(neat) 3 300,1 745,and 1 705cm-'; 6, (60MHz, CDCI,) 1.25 (3H, t), 1.50(9H, s), 3.90 (2 H, br, sharpens with D,O), 3.95 (2 H, s),4.05 (2H, q), 4.4(1H, br s, D,O exch.), and 7.15 (5 H, s); m/z 308 (M+),266,235,208 (base), 135,91, 57. t-Butyl 3-Benzyl-3-etho,uycarbon~lacetyl-2-(ethoxycarbonyl-methy1)carbazate(8b).-Acylation of the carbazate (7b) (3.97g,12.9mmol) with ethoxycarbonylacetyl chloride under the con- ditions described for compound (3a)gave the title compound (8b) (2.9g, 53) as a colourless gum, v,,,.(neat) 1 740,1 720, and 1 680cm-'; 6, (60MHz; CDCI,) 1.18 (3H, t), 1.32(3H, t), 1.43(9H, s), 3.65 (2 H, AB, J 16Hz), 3.90 (4 H, m), 4.20(2H, q), and 7.3 (5 H, s).89 I 1-Benzyl-2-(ethoxycarbonylmethyl)pyrazolidine-3,5-dione (4d).--The carbazate (8b) (0.6 g, 1.4mmol) was treated with TFA under the conditions described for compound (4b) to give the title compound(4)(0.36g, 92), m.p. 83 "C (Found: C, 60.95;H, 5.85;N, 10.2.Cl,Hl,N20, requires C, 60.H, 5.8;N, 10.1);v,,,.(Nujol) 1 755and 1 695cm-'; 6, (90MHz; CDCI,) 1.17(3H,t),3.34(2H,s),4.05(2H,q),4.17(2H7s),4.79(2H,s), and 7.30(5 H, m); m/z2'76(M'), 203 and 91 (base). t-Bury13-Ethoxycarbonylmethyl-2-methylcarbazate(7c).-A solution of benzyl chloroformate (4.7g, 27 mmol) in benzene (30ml) was added dropwise to a stirred ice-cooled solution of t-butyl 3-(ethoxycarbonylmethyl)carbazate (6.0g, 27 mmol) and triethylamine (2.79g, 27 mmol) in benzene (100 ml).The resulting suspension was stirred at room temperature for 12 h, and then filtered. The filtrate was evaporated under reduced pressure and the residue crystallised from ethanol to give t-butyl 3-benzyloxycarbonyl-3-(ethoxycarbonylmethy1)carbazate(7.0g, 7479,m.p. 120"C (Found: C, 57.9;H, 7.0;N, 7.9.C,,H,,N,O, requires C, 57.9;H, 6.9;N, 7.95);v,,,.(Nujol) 3 325,1 747,and 1 705cm-'. A stirred mixture of the above compound (5.0g, 14mmol), iodomethane (2.12 g, 15 mmol), and potassium carbonate (7.8g) in acetone was heated under reflux for 24 h.The mixture was filtered and the filtrate evaporated to give t-butyl 3-benzyloxy- carbonyl-3-ethoxycarbonylmethyl-2-methylcarbazate(4.8 g, 92) as a colourless oil. Without further purification, the above oil (2.76g) was dissolved in ethanol (70 ml) and hydrogenated over 10 palladiumxharcoal (0.08 g). The catalyst was filtered off, the filtrate evaporated, and the residue distilled to give the title compound (7c) (1.73g, 9973,b.p. 95-100 "C at 0.2mmHg (Kugelrohr) (Found: C, 51.6;H, 8.6;N, 11.8. C,,H,,N,O, requires C, 51.7;H, 8.7;N, 12.1);v,,,,(neat) 3 320,1 743,and 1 695cm-'; 6, (60MHz; CDCI,) 1.25(3H, t), 1.44 (9 H, s), 3.03 (3H, s), 3.61 (2 H, s), 4.17 (2 H, q), and 4.90 (1 H, br s); m/z232 (M'), 176,132,103,85, 76, 59, and 57 (base).t-Bury1 3-Ethoxycarbonylacetyl-3-etho.u~~carbonylmethyl-2-methylcarbazate (amp;).-Acylation of the carbazate (7c) (3.5g,15.1 mmol) with ethoxycarbonylacetyl chloride under the con- ditions described for compound (3a) gave the title compound (8c)(4.07g, 78) as a colourless oil, v,,,,(neat) 1 745,l 720, and 1 690cm-'; 6, (90MHz; CDCI,) 1.30(6H, t), 1.49 (9 H, s), 3.21 (3H,s),3.42(2H,AB,J13Hz),4.17(2H,AB,J17Hz),and4.22(4H, 4); m/z 346 (M+). 1-Etho.uycarbonylmethy1- 2-methylpyrazolidine- 3,5-dione (amp;).-The carbazate (8c) (3.95g, 11.4mmol) was treated with TFA under the conditions described for compound (4b) to give the title compound(4e) (1.45g, 63), m.p. 95.5"C (Found: C, 47.8;H, 6.0;N, 14.0.C,H,,N,O, requires C, 48.0;H, 6.0;N, 14.0);v,,,.(Nujol) 1 740and 1 695cm-'; 6, (90MHz; CDCI,) 1.38(3H, t), 3.12 (3H, s), 3.24 (2 H,s), 4.23 (2 H, q), and 4.37 (2 H, s); m/z200 (M+),127 (base), 99,and 85.t-Bury13-(Benzyloxycarbonyl)benzylidenecarbazate(5d).-A mixture of benzyl benzoylformate (1.0 g, 4.1mmol), t-butyl- carbazate (0.55g, 4.1mmol) and acetic acid (0.3ml) was heated under reflux for 3 h in ethanol (40 ml). The solvent was evaporated and the residue crystallised from a mixture of light petroleum (30ml) and ethanol (5 ml) to give the titlecompound(9)(1.20g, 8l), m.p. 131 "C (Found: C, 67.7;H, 6.2;N, 7.9. C,,H,,N,O, requires C, 67.8;H, 6.3;N, 7.9); v,,,.(Nujol)3 340,1 713,and 1 750cm-'; 6, (60MHz; CDCI,) 1.48 (9 H, s),5.17(2H, s), 6.98-7.70 (10 H, rn), and 1I .33(1H, br s);m/z 354 (M+).t-Butyl 3-(Benzyloxycarbonyl)benzylidene-2-methylcarbazate (6d).-Alkylation of the carbazate (W) (4.3g, 12 mmol) with iodomethane under the conditions described for compound (h) gave the title compound (6d) (4.25 g, 95) as a yellow oil, v,,,,(neat) 1735 and 1705 cm-'; 6, (60MHz; CDCl,) 1.44 (9H, s), 3.20(3 H, s), 5.21 (2 H, s), 7.32(8 H, m), and 7.68 (2 H, m);m/z 368 (M'). t-Butyl 3-(Benzyloxycarbonyl)benzyl-2-rnethylcarbazate (7d).-Reduction of the carbazate (6d) (2.25g) with sodium cyanoborohydride under the conditions described for com- pound (7a) gave the title compound (7d) (1.28 g, 57) as a colourless oil (Found: C, 68.4;H, 7.3;N, 7.6.C2,H2,N,04 requires C, 68.1;H, 7.1;N, 7.6); v,,,.(neat) 3 300,1 745,and 1 695cm-'; 6, (90MHz; CDCl,) 1.49 (9 H, s), 3.40 (3 H, s), 4.86 (1 H, br s, D,O exch.), 4.93(1 H, br s, sharpens with D20), 5.15 (2H, s), and 7.30(10H, m); m/z 370 (M') and 91 (base). t-Butyl 3-(Benzyloxycarbonyl)benzyl-3-ethoxycarbonyl-acetyl-2-rnethylcarbazate (8d).-Acylation of the carbazate (7d) (1.3g, 3.5 mmol) with ethoxycarbonylacetyl chloride under the conditions described for compound (3a) gave the title com- pound (8d)(0.85g, 50) as a colourless gum, v,,,,(neat) 1 740, 1 715,and 1690 cm-'; used without further purification.1-(Benzyloxycarbonyl)benzyl-2-methylpyrazolidine-3,5-dione (4f).-The carbazate (8d) (0.85g) was treated with TFA under the conditions described for compound (4b) to give the title compound (40 (0.55 g, 93) as a pale yellow gum (Found: C, 67.2;H, 5.2;N, 8.15.Cl,H,,N204 requires C, 67.45;H, 5.4;N, 8.3); v,,,.(neat) 1 745 and 1 710 cm-'; 6, (90MHz; CDC1,) 2.92(3 H, s), 3.19(2H, s), 5.29 (2 H, s), 6.22(1 H, s), and 7.32 (10H, m); m/z 338 (M'),203, 167, and 91 (base).t-Butyl 1 -Benzyloxy carbonylpyrazolidine-3-carboxylate (12).-A solution of diazomethane in ether was added to freshly distilled t-butyl acrylate (17.5 g, 0.136 mol) until a yellow colour persisted for 2 min. The ether was evaporated and the residue was immediately dissolved in ethanol (300 ml) and hydrogenated over 10 palladium-on-charcoal. The catalyst was filtered off, the filtrate evaporated, and the residue redis- solved in ethyl acetate (260ml). This solution was added to a solution of sodium hydrogen carbonate (24g) in water (260ml), and then the vigorously stirred ice-cooled mixture was treated with a solution of benzyl chloroformate (18.76g, 0.11mol) in ethyl acetate (50 ml).After 2h, the organic layer was separated, washed with dilute hydrochloric acid and water, dried, and evaporated. Chromatography of the residue gave (i) t-butyl4,5- dihydropyrazole-3-carboxylate (9)(9g, 39), v,,,.(neat) 3 300 and 1690 cm-'; and (ii) the title compound (12) (7.35 g, 18 overall); v,,,.(neat) 3 250,1 725,and 1 700 cm-'; 6, (60 MHz; CDCl,) 1.50(9H, s), 1.80-2.50 (2 H, m), 3.40-4.00 (2H, m), 4.50(2H, m), 5.23 (2 H, s), and 7.35(5 H, s).t-Butyl 1 -Benzyloxycarbonyl-2-(ethoxycarbonylacetyl)-pyrazolidine-3-carboxylate (13).-Acylation of the pyrazolidine (12) (2.5g, 8.1mmol) with ethoxycarbonylacetyl chloride under the conditions described for compound (3a)gave the title corn-pound (13) (2.9g, 84), m.p. 68"C (Found: C, 59.9;H, 6.7;N, 6.6.C, H2,N207 requires C, 60.0 H, 6.7;N, 6.7); v,,,.(Nujol)1 730 and 1 690cm-'; 6, (300 MHz; CDCl,) 1.22(3 H, t), 1.41 (9H, s), 2.23(1 H, m), 2.37(1 H, m), 3.20(1 H, m), 3.49 (2 H, AB, J 15 Hz), 4.11(3 H, m), 4.92(1 H, dd, J7.5,4.5Hz), 5.22 (2 H, AB, J 12 Hz), and 7.35(5 H, m); m/z 420 (M'). t-Butyl 2-(Ethoxycarbonylacetyl)pyrazolidine-3-carboxylate (14).-A solution of the pyrazolidine (13) (4.6g) in ethanol (100 mi) was hydrogenated over 10 palladium-on-charcoal(0.5 g).J. CHEM. SOC. PERKIN TRANS. I 1987 The catalyst was filtered off and the filtrate evaporated to give the title compound (14) (3.1 g, 9973,m.p. 65 "C(Found: C,54.6; H, 7.8;N, 9.8.C,,H2,N205 requires C, 54.5;H, 7.7;N,9.8); v,,,,(Nujol) 3 250, 1 735,and 1 650cm-'; 6, (250MHz; CDCl,) 1.27(3 H, t), 1.46 (9 H, s), 2.02(1 H, m), 2.54(1 H, m),2.86 (1 H, m), 3.19(1 H, m), 3.59 (2 H, AB, J 14 Hz), 3.62(1 H, m), 4.18 (2H q), and 4.40(1 H, dd, J 9, 7 Hz); m/z 286 (M'). t-Butyl 1,3-Dioxo-1 H-pyrazolo1,2-apyrazolidine-5-car-boxylate (4h).-A mixture of the pyrazolidine (14) (480mg) and sodium ethoxide from sodium hydride (44mg) in ethanol (20 ml) was heated under reflux for 8 h. The solvent was evaporated, and the residue partitioned between ether and water.The aqueous layer was separated, acidified, and extracted with dichloromethane. The CH2C12 extracts were dried, evaporated, and the residue crystallised from hexane-thy1 acetate to give the title compound (4h) (230mg, 57), m.p. 108 "C (Found: C, 54.8;H, 6.7;N, 11.5.C, 'H16N204 requires C, 55.0; H, 6.7;N, 11.7); vmax~(Nujol)1 735,1 705,and 1 690cm-'; 6, (250MHz; CDCl,) 1.49 (9 H, s), 2.46-2.78 (2 H, m), 3.39 (2 H, AB, J 20 Hz), 3.55 (1 H, m), 3.93(1 H, m), and 4.61(1 H, dd, J6,1 Hz); m/z 240 (M'), 184, 139 (base), 97,85, 83,and 57. 4-Diazopyrazolidine-3,5-diones(15): General Procedure.-Tri- ethylamine (1 mol equiv.) was added dropwise to a stirred ice- cooled solution of the pyrazolidine-3,5-dione (4) (1 mol equiv.) and toluene-p-sulphonyl azide (2 mol equiv.) in dichloro- methane or acetonitrile for compounds (4c) and (4h)l.The mixture was stirred at room temperature until t.1.c. indicated that no more pyrazolidinedione remained; the product diazo compounds are usually less polar, and show up very strongly under U.V. light. The reaction mixture was evaporated, and the residue triturated with ether. The insoluble toluene-p-sulphon- amide was filtered off and the ether washed with aqueous sodium hydroxide (5) and water, dried, and evaporated. The residue was purified by chromatography to give unchanged toluene-p-sulphonyl azide, followed by the diazo compound (15). The following compounds were prepared: 1 -Benzyl-4-diazo-2-methylpyrazolidine-3,5-dione(154 (42), m.p.58.5 "C (Found C, 57.6;H, 4.35;N, 24.4.ClIH,,N,02 requires C, 57.4;H, 4.4;N, 24.3); v,,,.(Nujol) 2 150,1 730,and 1 690cm-'; 6, (60MHz; CDCl,) 3.03(3 H, s), 4.75 (2 H, s), and 7.23(5 H, m); m/z 230 (M'), 204,and 91 (base).4-Diazo-1-diphenylmethyl-2-methylpyrazolidine-3,5-dione (15b) (63), m.p. 104.5 "C (Found: C, 66.75;H, 4.6;N, 18.4. C17H14N,0z requires C, 66.7;H, 4.6;N, 18.3); vmax.(Nujol)2 140and 1690 cm-'; 6, (60MHz; CDCl,) 2.90(3 H, s), 6.6 (1 H, s), and 7.30(10H, m); m/z 306(M'), 167(base), 152, 139, 115,and 91. l-Benzyl-4-diazo-2-phenylpyrazolidine-3,5-dione(1) (60), m.p. 136.5"C (Found: C, 65.6;H, 4.1;N, 19.25.C,,H,,N,O, requires C, 65.75;H, 4.1;N, 19.1); v,,,.(Nujoi) 2 150, 1 708, and 1 685 cm-'; 6, (60MHz; CDCl,) 4.70 (2 H, s) and 6.95-7.67(10H, m); m/z 292 (M+),266,and 91 (base).Ethyl (2-benzyl-4-diazo-3,5-dioxopyrazolidin-1 -yl)acetate (Ed) (51), m.p. 86 "C (Found: C, 55.7;H, 4.6;N, 18.5. Cl,H,,N,O, requires C, 55.6;H, 4.7;N,18.5); v,,,.(Nujol)2 150,1 745,and 1 690cm-'; 6, (90MHz; CDCI,) 1.18(3 H, t), 4.08(2 H, q), 4.17 (2 H, s), 4.73 (2 H, s), and 7.25(5 H, m); m/z 302 (M'), 200,155,and 91 (base). Ethyl (4-diazo-3,5-dioxo-2-methylpyrazolidin-1-yl)acetate (1s)(71), m.p. 63 "C (Found: C, 42.35;H, 4.4;N, 24.6. C,HloN404 requires C, 42.5;H, 4.7;N, 24.8); v,,,,(Nujol)2 140,1 745,1 720,and 1 680cm-'; 6, (90 MHz; CDCl,) 1.30 (3 H, t), 3.12(3 H,s), 4.23 (2 H, q), and 4.33 (2 H, s); m/z 226 (M'), 153, 127, 68, and 43.Benzyl(4-diazo-3,5-dioxo-2-methylpyrazolidin-1 -yl)(phenyl)- J. CHEM. SOC. PERKIN TRANS. I 1987 acetate (150 (49), m.p. 165.5 "C (Found: C, 62.5; H, 4.4; N, 15.2. C19H,,N404 requires C, 62.6; H, 4.4; N, 15.4); v,,,.(Nujol) 2 140, 1 740, and 1 687 cm-'; 6, (90 MHz; CDCI,) 2.72 (3 H, s), 5.34 (2 H, s), 6.22 (1 H, br s), and 7.30 (10 H, m); m/z 229 (base, M+ -CO,CH,Ph). t-Butyf 2-diazo-l,3-dioxo-hexahydro-lH-pyrazofo1,2-a-pyridazine-5-carboxylate (15g) (6873, m.p. 138 "C (Found: C, 51.2; H, 5.8; N, 19.8. C12H16N404 requires C, 51.4; H, 5.75; N, 20.0); v,,,,(Nujol) 2 120, 1 730, 1 713, and 1 690 cm-'; 6, (250 MHz; CDCI,) 1.46 (9 H, s), 1.5G1.95 (3 H, m), 2.32 (1 H, m), 3.01 (1 H, dt, J 13,3 Hz), 4.14 (1 H, m), and 4.73 (1 H, m); m/z 280 (M+),224, 179 (base), 151, 83, 55, and 41.t-Butyf 2-diazo- 1,3-dioxo- 1 H-pyrazofo 1,2-alpyrazolidine-5- carbo.uylute (15h) (63), m.p. 107 "C (Found: C, 49.6; H, 5.2; N, 21.0. C, ,H 14N404 requires C, 49.6; H, 5.3; N, 21.0); vmax,(Nujol)2 130, 1 740, and 1 670 cm-'; 6, (250 MHz; CDCI,) 1.48 (9 H, s), 2.47-2.59 (1 H, m), 2.67 (1 H, m), 3.57 (1 H, dt, J 11.7 Hz); 3.85 (1 H, m), and 4.56 (1 H, dd, J 11.7 Hz); m/z 266 (M'), 210, 165, 87, and 57 (base). Photofysis of the Diazo Compound (15a).-(a) In ether and ethanol. A solution of the diazo compound (15a) (731 mg) in dry ether (300 ml) and ethanol (20ml) was irradiated for 4.5 h. Evaporation of the solvents and chromatography of the residue gave (i) diethyl malonate (130 mg, 26) and (ii) a mixture of the diazetidinones (16a; Nu = EtO) and (17a; Nu = EtO) (234 mg, 30) in the ratio 1 :1 by n.m.r.This mixture was re- chromatographed to give (i) ethyl 2-benzyf- 1-methyf-3-0x0- 1,2-dia~etidine-4-carboxyfate(16a; Nu = EtO) (78 mg) as a colourless oil, v,,,.(neat) 1 783 cm-'; 6, (250 MHz; CDCI,) 1.30 (3 H, t), 2.58 (3 H, s), 4.28 (2 H, qq), 4.37 (1 H, s), 4.59 (2 H, AB, J 15.7 Hz), and 7.35 (5 H, m); m/z 249 (M+ + H), 175, 147, 133, 106, 91 (base), 77, 65, and 42; (ii) a mixture of the diazetidinones (16a; Nu = EtO) and (17a; Nu = EtO) (89 mg); and (iii) ethyl 1-benzyf-2-methyf-3-oxo- 1,2-diuzetidine-4- carbo-qhte (17a;Nu = EtO) (67 mg) as a yellow gum (Found: M' 248.1 158. C, 3H ,N,O, requires 248.1 160); v,,,,(neat) 1 785 and 1 747 cm-'; 6, (250 MHz; CDCI,) 1.25 (3 H, t), 2.92 (3 H, d, J0.65 Hz), 4.01 (2 H, AB, J 12.5 Hz), 4.20 (2 H, q), 4.47 (1 H, d, J 0.65 Hz), and 7.40 (5 H, m); m/z 248 (M'), 234, 192, 174, 147, 117, 91 (base), 65, and 43.(b) In M'et ether. A solution of the diazo compound (15a) (3 12 mg) in wet ether (200 ml) was irradiated for 3.25 h. The mixture was extracted with aqueous potassium hydrogen carbonate and the aqueous layer then acidified, and extracted with dichloro- methane. The CH,CI, extracts were dried and evaporated to give a mixture of 2-benzyl-1-methyl-3-oxo- 1,2-diazetidine-4- carboxylic acid (16a; Nu = HO) and 1-benzyl-2-methyl-3-0x0-1,2-diazetidine-4-carboxylicacid (17a;Nu = HO) (97 mg, 33) in the ratio 1 :1 by n.m.r.; v,,,,(neat) 3 5-2 400, 1 783, and 1 745 cm-I; 6, (90 MHz; CDCI,) for (16a;Nu = HO) 2.59 (3 H, s), 4.52 (3 H, m), 7.28 (5 H, m), and 9.26 (1 H, br s); for (17a; NU = HO) 2.88 (3 H, s), 4.02 (2 H, AB, J 13 Hz), 4.42 (1 H, s), 7.28 (5 H, m), and 9.26 (1 H, br s).Photofysis of the Diazo Compound (Fib).-(a) In ether and ethanol. A solution of the diazo compound (15b) (634 mg) in dry ether (300 ml) and ethanol (20 ml) was irradiated for 4.5 h. The solvent was evaporated and the residue chromatographed to give (i) diethyl malonate (99 mg, 30) and (ii) a mixture of the diazetidinones (16b;Nu = EtO) and (17b;Nu = EtO) (246 mg, 36) in the ratio 1: 1 by n.m.r. This mixture was re-chromatographed to give (i) ethyl 1-diphenyfmethyf-2-methyf-3-o.uo-l,2-diazetidine-4-car~o~~~fa~e(17b; Nu = EtO) (40 mg) as a colourless oil, v,,,,(neat) 1 785 and 1742 cm-'; 6, (250 MHz; CDCI,) 1.22 (3 H, t), 2.53 (3 H, d, J 0.65 Hz), 4.13 (2 H, qq), 4.42 (1 H, d, J 0.65 Hz), 4.68 (1 H, s), 7.18-7.42 (6 H, m), and 7.45-7.60 (4 H, m); m/z 324 (M+),266, 251, 247, 238, 223, 192, 167 (base), 152, and 91; (ii) a mixture of diazetidinones (16b;Nu = EtO) and (17b Nu = EtO) (170 mg); and (iii) ethyl 2-diphenyfmethyf- 1 -methyf-3-oxo- 1,2-diazetidine-4-carboxyfute (16b; Nu = EtO) (32 mg) as a colourless oil (Found: M' 324.1477.C,,H,,N,O, requires 324.1472); v,,,.(neat) 1 783 and 1 742 cm-'; 6, (250 MHz; CDCI,) 1.28 (3 H, t), 2.51 (3 H, s), 4.26 (2 H, q), 4.32 (1 H, s), 5.93 (1 H, s), and 7.1 5-7.52 (10H, m); m/z 324 (M'), 167 (base), 165, 152, and 77.(b) In M'et ether. A solution of the diazo compound (15b) (534 mg) in wet ether (300 ml) was irradiated for 4.5 h. Extractive work-up as described above gave a mixture of 2-di- phenylmethyl- 1 -methyl-3-oxo- 1,2-diazetidine-4-carboxylicacid (16b; Nu = HO) and 1-diphenylmethyl-2-methyl-3-0~0-1,2-diazetidine-4-carboxylic acid (17b;Nu = HO) (168 mg, 33) in the ratio 1: 1 by n.m.r., v,,,,(neat) 3 6-2 500, 1 765, and 1 720 cm-I; 6, (60 MHz; CDCI,) 2.50 (s), 4.37 (s),4.70 (d), 5.90 (s), 7.1-7.6 (m), and 8.5 (br s). This mixture of carboxylic acids (98 mg) was dissolved in benzene (20 ml) and heated under reflux for 4 h. Evaporation of the solvent and chromatography of the residue gave a mixture of the diazetidinones (18a) and (19a) (80 mg, 95) in the ratio 1 :1 by n.m.r.This mixture was rechromatographed to give (i) 1-diphenyfmethyf-2-methyf-1,2-diazetidin-3-one (19a) (39 mg), m.p. 135 "C (Found: C, 76.3; H, 6.2; N, 10.8. Cl,H,,N20 requires C, 76.2; H, 6.4; N, 11.1); v,,,~(Nujol) 1 765 cm-'; 6 (250 MHz; CDCI,) 2.46 (3 H, d, J0.8 Hz), 3.72 (1 H, dd, J 13.5, 0.8 Hz), 4.32 (1 H, d, J 13.5 Hz), 4.57 (1 H, s), 7.1 7-7.38 (6 H, m), and 7.40-7.52 (4 H, m); mjz 252 (M+),209, 182, 167 (base), 152, 132, 104, 85, 77, and 43; (ii) 2-diphenyfmethyf-l-methyl-1,2-diuzetidin-3-one (18a) (37 mg) (Found: C, 76.0; H, 6.4; N, 11.1); v,,,,(NuJol) 1 768 cm-'; 6, (90 MHz; CDCI,) 2.46 (3 H, s), 4.06 (2H,AB,J13.6Hz),5.91 (1 H,s),and7.2amp;-7.50(10H,m);m/z 252 (M'), 167 (base), 166, 152, and 91.Photofysis of the Diazo Compound (15c).-(a) In ether and ethanol. A solution of the diazo compound (1) (740 mg) in dry ether (300 ml) and ethanol (25 ml) was irradiated for 3.3 h. Evaporation of the solvents and chromatography of the residue gave a mixture of the diazetidinones (16c; Nu = EtO) and (17c; Nu = EtO) (580 mg, 72) in the ratio 1.7: 1 by n.m.r. This mixture was re-chromatographed to give (i) ethyl 1-benzyl-3-oxo-2-phenyf-1,2-diazetidine-4-carboxyfate(17c; Nu = EtO) (26 mg) as colourless needfes, m.p. 71.5 "C (Found: C, 70.0; H, 5.75; N, 9.0. C18H18N20, requires C, 69.7; H, 5.85; N, 9.0); v,,,.(NuJol) 1780 and 1758 cm-'; 6, (90 MHz; CDCI,) 1.19 (3 H, t),4.16 (2 H, q), 4.20 (2 H, AB, J 13 Hz), 4.54 (1 H, s), and 6.9Ck7.36 (10 H, m); m/z 310 (M+)and 91 (base); (ii) a mixture of diazetidinones (361 mg); and (iii) ethyl 2-benzyf-3-oxo- 1-phenjlf-1,2-diazetidine-4-carbo.u~fate(16c; Nu = HO) (163 mg), v,,,,(neat) 1 785 and 1 750 cm-'; 6, (90 MHz; CDCI,) 1.28 (3 H, t),4.26(2H,q),4.67(2H,AB,J16Hz),4.82(1H,s),6.90-7.10 (2 H, m), and 7.13-7.47 (10 H, m); m/z 310 (M+),205, 104 (base), 91, and 77.(b) In wet ether. A solution of the diazo compound (1) (740 mg) in wet ether (300 ml) was irradiated for 4 h. Extractive work- up gave a mixture of 2-benzyl-3-0x0- 1-phenyl- 1,2-diazetidine-4- carboxylic acid (16c; Nu = HO) and l-benzyl-3-oxo-2-phenyl-1,2-diazetidine-4-carboxylicacid (17c; Nu = HO) (397 mg, 55) in the ratio 1.6: 1 by n.m.r., v,,,.(neat) 3 600-2 400 and 1780--1 730br cm-'; 6, (250 MHz; CDCI,) for (16c; Nu = HO) 4.59 (2 H, AB, J 15 Hz), 4.76 (1 H, s), 6.93-7.40 (m), and 9.55 (br s); for (17c; Nu = HO) 4.15 (2 H, AB, J 13 Hz), 4.65 (1 H, s), 6.93-7.40 (m), and 9.55 (br s).The mixture of carboxylic acids (230 mg) was dissolved in benzene (30 ml) and heated under reflux for 2 h. Evaporation of the solvent and chromatography of the residue gave an inseparable mixture of 2-benzyl- 1-phenyl- 1,2-diazetidin-3-one (1Sb)and 1-benzyl-2-phenyl- 1,2-diazetidin-3-one (19b)(185 mg, 894 J. CHEM. SOC. PERKIN TRANS. I 1987 Table 3. Atom co-ordinates (x lo4) for (1) Atom Y 6051(5) 7 602(4) 5 496(5) 3 424(5) 2 503(4) 2 630(4) I 631(4) 721(5) 2 670(5) 3 610(5) 4 394(4) 6 737(6) 7 791(8) 3 536(4) 5 570(3) 2 646(3) 4 197(5) 6 257(6) 2 469(7) 5 159(8) I' 3 814(1) 4 124(1) 3 809(1) 3 391(1) 3 232(1) 3 189(1) 2 524( 1) 2 463( 1) 2 659(1) 3 357(1) 3 385(1) 4 125(1) 4 403(2) 2 2 139(1) 1396(1) 793( 1) 805(2) 237(2) 763(2) Table 6.Atom co-ordinates ( x lo4) for (17c) r v 674( 2) 7 462(3) I 522(2) 6 320(3) 1 544(2) 6 328(4) 1 997(1) 5 543(3) 722(2) 7 622(4) 1798(2) 5 201(3) 2 533(2) 4 087(4) 2 834(3) 2 981(5) 2 412(3) 3 1681(3) 4 102(4) 1370(2) 5 213(4) 1003(2) 8 972(4) 180( 2) 10 207(4) 339(3) 11 612(4) -41 5(3) 12 725(4) -1 351(3) 12 439(4) -1 519(3) 1 1 025(5) -750(3) 9 924(4) -215(2) 7 161(4) -928(2) 6 513(4) -135(1) 7 541(3) -986(3) 7 145(5) -701(3) 7 530(6) Table 7.Bond lengths (A) for (17c) 1.473(3) 1.489(4) 1.392(4) I .53 l(4) 1.377(4) 1.376(5) 1.367(6) 1.506( 4) I .362(5) 1.355(6) 1.380(5) I .3 17(4) 1.449(6) Table 8. Bond angles (") for (17c) 87.6( 2) 11 1.6(2) 125.7(2) 133.2( 3) 136.6(3) 115.4(3) 1 18.6(3) 120.1 (3) I20.0(3) 120.2( 3) I07.9(2) I20.0(3) 121.1(4) 1 18.3(4) 120.8(4) 110.2(3) 1 17.6(3) 2 572(2) 3 127(2) 1451(2) 1 144(2) 277(2) 2 076(2) 2 197(2) 3 273(2) 4 133(2) 3 945(2) 2 905(2) 8W2)238(3) 1988(2) 1776(2) 2 079(2) 1991(2) 2 849(3) 2 172(4) 938(3) 3 360(2) 3 485(2) 2 593(2) 2 160(1) 2 395(2) 4 187(2) 4 150(2) 4 841(3) 5 565(3) 5 6ow)4 9w2) 3 882(2) 3 590(2) 3 194(3) 2 93 I(3) 3@w)3 442(3) 3 725(3) 1703(2) 1 862(2) 881(2) 114(3) -721(2) 1.488(4) 1.362(4) 1.2OO(4) I .493(4) 1.365(4) 1.363(6) 1.384(4) 1.352(5) 1.369(5) 1.366(6) 1.190(4) I .468(4) I10.2(2) 94.6(2) 134.0(3) 90.1(2) 87.3(2) 1 15.0(2) 12 1.3( 3) 1 19.9(3) 120.3(3) 119.6(3) 12 1.6(3) 118.3(3) 12 1.2( 4) 120.3(4) 125.5(3) 124.3(3) 108.I(3) mg), the ratio of the diazetidinones being ca. 2.5: 1 by n.m.r., 6, (90 MHz; CDCI,) infer afia 1.23 (t), 1.32 (t), 3.47(AB,J 16 Hz), 3.79 (s), 3.82 (s), 3.91 (AB, J 18 Hz), 4.0-4.3 (m), 4.40 (AB,J, 11.5 Hz), 4.77 (m), 6.78(s), and 7.35 (m).(b) In wet ether. A solution of the diazo compound (la)(222 mg) in wet ether (250mi) was irradiated for 4 h. Extractive Table 4. Bond lengths (A) for (1) 1.224( 3) 1.353(3) 1.296(4) 1.376(4) 1.420(3) 1.52l(4) 1.523(4) 1.1 19(5) 1.325(3) 1.496(4) 1.501(5) Table 5. Bond angles (") for (15g) 1303 3) 10342) 124.8(3) 130.4(3) 125.4(3) 108.6(2) 109.4(2) 1 13.5(2) 110.5(2) I1 1.5(2) 1 16.0(2) 123.5(2) 125.8(2) 109.0(2) 109.9(3) 110.9(3) 1.440(4) 1.437(4) 1.21 7(4) 1.459(3) 1.52l(4) 1.509(4) 1.445( 3) 1.205(3) 1.492( 3) 1.498(4) 126.1(3) I 1 1.0(2) 124.2(3) 104.2(2) 12 1.2(2) 114.1(2) 109.8(2) 11 1.8(2) 108.6(2) 126.1(2) 179.3(4) 110.7(2) 12 1.7(2) 102.7(2) 110.8(2) 1 13.2(3) 95) in the ratio 1.6:1 by n.m.r., v,,,.(neat) 1 770cm-'; 6, (250 MHz; CDCI,) for (18b) 4.48 (2 H, br s), 4.61(2H,s), and 6.9-7.4(m); for (19b)4.06(2H,AB,J 12.5Hz), 4.09(2 H, AB,J 14 Hz), and 6.9-7.4 (m); m/z 238 (M+),210, 132, 118, 105, 91 (base), and 77.Photolysis of the Diazo Compound (15d).-(a) In ether and methanol. A solution of the diazo compound (1s)(330mg) in ether (350ml) and methanol (30 ml) was irradiated for 4 h. Evaporation of the solvents and chromatography of the residue gave an inseparable mixture of the hydrazone (20) and the diazetidinones (16d; Nu = MeO) and (17d; Nu = MeO) (250 work-up gave a mixture of 1-benzyl-2-ethoxycarbonylmethyl- J. CHEM. SOC. PERKIN TRANS. I 1987 Table 9.Atom co-ordinates ( x lo4) for (24) Atom Y 4' 898( 2) 907m 7 ow2) 5 649(3) 5 922(2) 6 059(2) 351(2) 1818(2) 2 472(2) 2 493(2) 2 677(2) 1839(2) 1924(2) 4 916(2) 5 584(2) 4 703(2) 4 954(2) 6 274(2) 7 026(2) 6 858(2) 6 179(1) 5 998( 1) 5 853(2) 4 934(2) 4 834(2) 4 935(2) 5 862( 1) 3 559(2) 3 766(2) 4 226( 1) 5 347(2) 4 691(2) 5 218(2) 4 054(2) 3 929(3) 6 661(2) 7 360(1) 6 486( 1) 7 151(2) 5 445(3) 5 850(3) 5 771(3) 952(2) 898(2) 1035(2) 1272(2) 1401(2) 3 408(4) 5 122(4) 3 080(4) 7 779(3) 7 357(2) 8 990(2)9 399(2) 10 533(2) 8 038(3) 7 301(4) 6 682(3) 6 701(2) 7 370(1) 6 627( 1) 5 941(1) 5 893(2) 1 249(2) 1 1 469(3) 6 485(2) 630(3)1025(3) 1 728(2) 1627(2) 2 152(2) 2 676(2) 3 066(4) 3 578(3) 1904(3) 10974(3) 9 782(3) 10 976(2) 12 022(2) 10 164(2) 10 502(2) 9 318(3) I1 315(4) 11 037(4) 6 957(2) 7 345(2) 5 191(2) 4 980(2) 4 866( 1) 4 272(2) 4 105(3) 4 807(3) 3 396(2) Table 10. Bond lengths (A) for (24) 1.538(4) 1.501(4) 1.505(4) 1.208(4) 1.334(4) 1.437(4) 1.461(3) 1.53 l(4) 1.525(3) 1.522(4) 1.517(5) 1.468(4) 1.197(4) 1.306(4) I .485( 3) 1.503( 6) I .482(5) 1.494(6) 1.214(4) I .37 l(4) 1.37l(4) 1.469(4) I .290(3) 1.498(4) 1.488(5) 1.494( 6) 1.478(4) 1.21 l(3) 1.318(4) 1.495(4) 1.505(5) 1.498(4) 1.490(4) 3-0x0-1,2-diazetidine-4-carboxylicacid (la;Nu = HO) and 2-benzyl-1-ethoxycarbonylmethyI-3-oxo-1,2-diazetidine-4-carboxylic acid (17d; Nu = HO) (101 mg, 47) in the ratio 2.8: 1 by n.m.r., v,,,.(neat) 3 600-2 450, 1 790, and 1 750 cm-'; 6, (90 MHz; CDCI,) major isomer 1.23 (3 H, t), 3.84 (2 H, AB, J 185Hz),4.10(2H,brs),4.12(2H,q),4.71(1 H,s),7.36(5H,s), and 8.39 (1 H, br s, D20exch.); for minor isomer 1.23 (3 H, t), 3.56 (2 H, AB, J 16.5 Hz), 4.12 (2 H, q), 4.62 (2 H, AB, J 15 Hz), 4.78 (1 H, s), 7.36 (5 H, s), and 8.39 (1 H, br s, D20 exch.). This mixture of carboxylic acids (48 mg) was dissolved in benzene (10 ml) and heated under reflux for 5 h.Evaporation of the solvent and chromatography of the residue gave (i) 1-benzyl-2-etho.uycarbonylmethyl-1,2-diuzetidin-3-one(1) (28 mg) as a colourless liquid which could not be completely purified (Found: C, 63.5; H, 6.8; N, 10.8. CI I 6N,03 requires C, 62.9; Table 11. Bond angles (") for (24) 87.1(2) 116.8(2) I14.8(2) 137.0(3) 89.5(2) 133.5(3) 139.2(2) 97.0(2) 122.1(2) 1083 2) 1 10.0(2) 113.7(3) 11 1.0(2) 110.6(3) 108.6(2) 86.4(2) I 13.5(2) 108.1(2) 123.4( 3) 11 1.6( 2) 124.9(2) 122.3(2) 1 I0.9( 3) 108.5(3) 110.7(3) 103.1(2) 1 10.4(3) 1 12.9(4) 12 143) 117.9(3) 120.3( 3) 11732) 119.8(3) 122.1(2) 1 17.8(2) 126.0(3) 118.2(3) 1 I5.8(2) 110.2(2) 1 10.9( 3) 109.8(3) 120.1(3) 114.9(2) 124.9( 3) 121.3(2) 102.4(3) 108.3(3) 1 10.8( 3) 110.8(3) 1 10.8( 3) 1 13.2(3) H, 6.5; N, 11.3); v,,,.(neat) 1 780 and 1 745 cm-'; 6, (250 MHz; CDCI,) 1.26 (3 H, t), 3.82 (2 H, AB J 18 Hz), 3.97 (2 H, AB, J 12 Hz), 4.17 (2 H, q), 4.18 (2 H, AB, J 14 Hz), and 7.34 (5 H, m); m/z 248 (M'), 175,147,133,106, and 91 (base); and (ii) 2-benzyl-1-etho.uycarbonylmethyl- 1,2-diazetidin-3-one (Iamp;) (10 mg) as a colourless liquid (Found: M', 248.1 155.CI3Hl6N20, requires M, 248.1 160); v,,,,(neat) 1 770 and 1 745 cm-'; 6, (250 MHz; CDCI,) 1.21 (3 H, t), 3.42 (2 H, AB, J 16 Hz), 4.10 (2 H, q), 4.26 (2 H, AB, J 14 Hz), 4.57 (2 H, AB, J 16 Hz), and 7.35 (5 H, m); m/z 248 (M+),192, 175, 162, 147, 118, and 91 (base). Photolysis of Diazo Compound (1) in Ether and Methanol.- A solution of the diazo compound (15e) (90 mg) in dry ether (100 ml) and methanol (5 ml) was irradiated for 4 h. Evaporation of the solvents and chromatography of the residue gave an inseparable mixture of the hydrazone (21) and the diazetidinones (16e; Nu = MeO) and (17e; Nu = MeO) (46 mg). From this mixture the hydrazone (21) could be crystallised as colourless crystals, m.p.94 "C (Found: C, 46.2; H, 7.8; N, 21.55. C,H,,N,02 requires C, 46.1; H, 7.7; N, 21.5); v,,,,(Nujol) 3 300 and 1 690 cm-'. The n.m.r. spectrum of the remaining mixture showed: hydrazone (21) 6, (90 MHz; CDCI,) 1.34(3H,t),2.96(3H,d,J5Hz),4.29(2H,q),6.68(1H, s), and 6.83 (1 H, br s); major diazetidinone (Iamp;; Nu = MeO) 6, 1.28 (3 H, t), 2.82 (3 H, s), 3.88 (3 H, s), 4.1 1 (2 H, s), 4.22 (2 H, q), and 4.50 (1 H, s); minor diazetidinone (17e; Nu = MeO) 6, 1.28 (3 H, t), 3.10 (3 H, s), 3.70 (2 H, AB, J 15 Hz), 3.83 (3 H, s), 4.22 (2 H, q), and 4.76 (1 H, s). The ratio of diazetidinones was ca. 2:l. Photolysis of the Diazo Compound (150 in Wet Ether.-A solution of the diazo compound (150 (175 mg) in wet ether (200 ml) was irradiated for 8 h.Extractive work-up gave a colourless oil (67 mg) which could not be identified. Photolysis of the Diazo Compound (15g).-(a) In ether and ethanol. A solution of the diazo compound (1) (1.OO g) in dry ether (300 ml) and ethanol (25 mi) was irradiated for 3 h. Evaporation of the solvents and chromatography of the residue J. CHEM. SOC. PERKIN TRANS. I 1987 p = 95.82( l)", U = 1 409 A3,~(CU-K,)= 8 cm-', X = 1.541 78 A, space group P2,/n, Z = 4, D,= 1.32 g ern-,, F(000) = 592. Approximate crystal dimensions 0.22 x 0.17 x 0.15 mm; compound (17c) C18H18N203,M = 310.4, monoclinic, a = 13.711(2), b = 8.281(1), c = 15.172(2) A, p = 104.31(1)", U = 1669 A3, ~(CU-K,)= 7 cm-', X = 1.541 78 A, space group P2,/n, Z = 4, D, = 1.24 g cm-,, F(000) = 656.Approxi-mate crystal dimensions 0.30 x 0.30 x 0.15 mm; compound (24) C21H32N,06, if = 436.5, monoclinic, a = 14.104(2), b = 11.200(2), c = 16.217(4) A, = 115.69(1)", U2 308 A,, ~(CU-K,)= 7 cm-', 1 = 1.541 78 A, space group P2,/c, 2 = 4, D,= 1.26 g cm-,, F(000) = 936. Approximate crystal dimensions 0.38 x 0.25 x 0.20 mm. Data Collection and Processing.-Compound (15g) 1 452 independent measured reflections (0 6 SO0), 1290 observed IFJ 3o(lF,l); (17c) 1 71 1 independent measured reflections (0 6 SO"), 1 454 observed; compound (24) 2 367 independent measured reflections (8 d 50"), 2 155 observed. All data measured on a Nicolet R3m diffractometer with Cu-K, radiation (graphite monochromator) using a-scans. Structure Analysis and ReJinement.-All three structures were solved by direct methods and their non-hydrogen atoms refined anisotropically.In structure (17c) the position of the C(4) hydrogen atom and in (24) the C( 1) hydrogen atom were deter- mined from AF maps and were allowed to refine isotropically. The other hydrogen atom positions, in all three structures, were idealised (C-H = 0.96 A), assigned isotropic thermal para- gave (i) diethyl malonate (258 mg, 46), and (ii) an oily solid from which crystallised, t-butyl ethyl hexahydro-2-0~0- 1,2-diazeto 1,2-alpyridazine-4,1 -dicarboxylate (16g; Nu = EtO) (123 mg, 12) as colourless needles, m.p. 136-138 "C (from ethanol-light petroleum) (Found: C, 56.1; H, 7.5; N, 9.5.C14H2,N205 requires C, 56.4; H, 7.4; N, 9.4); v,,,.(Nujol) 1 780, 1 762, and 1 733 cm-'; 6, (300 MHz; CDCI,) 1.32 (3 H, t), 1.48 (9 H, s), 1.52-2.00 (3 H, m), 2.24 (1 H, br d, J 13.5 Hz), 2.39 (1 H, dt, J 13,2.4 Hz), 3.42 (1 H, dt, J 10,2.4 Hz), 4.29 (2 H, qq), 4.43 (1 H, s), and 4.47 (1 H, d, J 6.4 Hz); 6, (75.5 MHz; CDCI,) 14.2 (q), 20.9 (t), 23.2 (t), 27.9 (q), 53.2 (d), 56.2 (t), 61.9 (t), 80.3 (d), 82.7 (s), 156.3(s), 164.4(s), and 167.2 (s); m/z 298 (M+),242, 197, 169, (base), 141, 114, 97, and 57. The mother liquors from the above crystallisation were evaporated and the residue recrystallised from light petroleum to give t-butyl 1,4,5,6-tetrahydropyridazine-3-carboxylate(23) (310 mg, 4773, m.p. 92 "C (Found: C, 58.4; H, 9.15; N, 14.9.C9H16N202 requires C, 58.7; H, 8.75; N, 15.3); v,,,.(NuJol) 3 335, 1 688, and 1 600 cm-'; 6, (90 MHz; CDCl,) 1.50 (9 H, s), 1.70-2.16 (2 H, m), 2.40 (2 H, t), 3.19 (2 H, br t), and 6.83 (1 H, br s, D20exch.). (b) Zn wet ether. A solution of the diazo compound (15g) (1.30 g) in wet ether (300 ml) was irradiated for 7 h. Hydrogen carbonate extraction and acidification gave t-butyl hexahydro- 2-0x0- 1,2-diazeto 1,2-apyridazine-4-carboxylate-1 -carboxylic acid (16g; Nu = HO) (196 mg, 14), m.p. 109-1 11 "C, which could not be obtained analytically pure due to its facile decarboxylation, vmax,(NuJol) 3 5-2 500, 1 758, and 1 725 cm-I;6,(300 MHz; CDCl,) 1.47 (9 H, s), 1.58-2.00 (3 H, m), 2.23 (1 H, d, J 12.5 Hz), 2.54 (1 H, td, J 10,2.5Hz), 3.44 (1 H, d, J meters U(H) = 1.2Ue,(C), and allowed to ride on their parent 10 Hz), 4.58 (1 H, s), 4.62 (1 H, d, J7 Hz), and 8.33 (1 H, br s); carbon atoms.All the methyl groups were refined as rigidmi-7 270 (M+), 226, 214, 169, 141, 125, 97 (base), 57, and 41. bodies. Refinement was by block-cascade full-matrix least- The ether layers from the hydrogen carbonate extraction were 0.043, R, =squares and converged to give for (15g) R = (w' = 02(F) + 0.000 34F2), for (17c) R = 0.048, R, = 0.057 (w' = 02(F) + 0.054 (w' 02(F)+ evaporated, and the residue chromatographed to give the tetra- hydropyridazine (23) (360 mg, 48). The carboxylic acid (16; Nu = HO) (82 mg) was dissolved 0.00061F2) and for (24) R = 0.046, R, = O.OO0 49F2).Computations were carried = in benzene (15 ml) and heated under reflux for 2 h. Evapor- out using the SHELXTL program system. ation of the solvent and chromatography of the residue gave t-butyl hexahydro-2-0x0- 1,2-diazeto 1,2-alpyridazine-4- carboxylate (18d) (1 1 mg, 16) as an oil (Found: M+,226.1326. c, H 8N203 requires M, 226.13 17); v,,,.(neat) 1 765 and 1 735 cm-'; 6, (300 MHz; CDCI,) 1.47 (9 H, s), 1.58-1.86 (3 H, m), 2.18(1 H,d, J12.5 Hz),2.27(1 H,m),3.31 (1 H,dt, J, 10,2.5Hz), 4.08 (2 H, AB, J 13 Hz), and 4.59 (1 H, d, J 6.5 Hz); m/z 226 (M+),142, 125, 97 (base), 85, 83, 57, and 41. (c) In dry ether. A solution of the diazo compound (15g) (600 mg) in dry ether (250 ml) was irradiated for 5 h.Evaporation of the ether and chromatography of the residue gave (i) the tetrahydropyridazine (23) (210 mg, 5 lx), and (ii) t-butyl 1-(3-i-butoxycarbonyl- 1,4,5,6- tetrahydropyridazin- 1 -yl )carbony/ -hexahydro-2-0x0- 1,2-diazeto 1,2-apyridazine-4-carboxylate (24) (130 mg, 1 l), m.p. 163 "C (Found: C, 57.7; H, 7.4; N, 12.7. C21H,,N406 requires C, 57.8; H, 7.4; N, 12.8); vmax~(NuJol) 1 778, 1 740, 1 690, and 1 595 cm-'; 6, (300 MHz; CDCI,) 1.47 (9 H, s), !.52 (9 H, s), 1.57-2.00 (5 H, m), 2.20 (1 H, br d, J 12.5 Hz), 2.47 (3 H, m), 3.76 (3 H, m), 4.62 (1 H, d, J6.5 Hz), and 5.30 (1 H, m); m/z 436 (M+),380,307 (base), 279 251,224, 197, 196, 169, 124, 111, 100, 83, 57, and 41. Photoljvsis of the Diazo Compound (15h) in Ether and Ethanol.-A solution of the diazo compound (15h) (24 mg) in ether (100 ml) and ethanol (10 ml) was irradiated for 1.5 h.Evaporation of the solvents gave a mixture of diethyl malonate and a brown gum (19 mg), v,,,, 1 730 cm-' of unknown composition. Crystal Data.-Compound (15g) C 2H 6N404, M = 280.3, monoclinic, a = 5.482(1), b = 20.108(3), c = 12.840(2) A, Fractional atomic co-ordinates for the non hydrogen atoms for (15g) are given in Table 3. Tables 4 and 5 list the bond lengths and angles respectively. Fractional atomic co-ordinates for (17c) are given in Table 6. Tables 7 and 8 list the bond lengths and angles respectively. Fractional atomic co-ordinates for (24) are given in Table 9. Tables 10 and 11 list the bond lengths and angles respectively. The fractional co-ordinates of the hydrogen atoms and isotropic thermal parameters, and the thermal parameters for the non-hydrogen atoms for (15g), (17c), and (24) are available on request from the Cambridge Crystallographic Data Centre.* Acknowledgements We thank the S.E.R.C.and Roche Products Ltd. for a CASE award to C. J. P. * See Instructions for Authors (1987), para. 5.6.3 in J. Chem.Soc., Perkin Trans. I, 1987, Issue 1. References 1 G. Lawton, C. J. Moody, and C. J. Pearson, preceding paper. 2 G. Lowe and D. D. Ridley, J.Chem.Soc., Perkin Trans. I, 1973,2024; G. Stork and R. P. Szajewski, J. Am. Chem. SOC.,1974, 96, 5787; E. Voigt and H. Meier, Chem. Ber., 1975, 108, 3326. 3 H. Chaimovich, R. J. Vaughan, and F. H. Westheimer, J. Am. Chem. SOC.,1968, 90, 4088; R. R. Rando, ibid., 1970, 92, 6706; N. T. Buu and J. T. Edward, Can. J. Chem., 1972, 50, 3719; E. Muller and P. Heinrich, Chem. -Zfg., 1971, 95, 567; ibid., 1972, , 112; H. Tomioka, M. Kondo, and Y. Izawa, J. Org. Chem., 1981,46,1090. J. CHEM. SOC. PERKIN TRANS. I 1987 4 Preliminary communication, C. J. Moody, C. J. Pearson, and G. Lawton, Tetrahedron Lett., 1985, 26, 3167. 5 W. Streicher and H. Reinshagen, Chem. Ber., 1975, I@, 813. 6 C. H. Hassall, A. Krohn, C. J. Moody, and W. A. Thomas, J. Chem. Soc., Perkin Trans. I, 1984, 155; C. H. Hassall, G. Lawton, and C. J. Moody, Eur. fat.Appl., EP42100, 1981. 7 C. J. Moody, C. J. Pearson, and G. Lawton, Tetrahedron Lett., 1985, 26, 3 17 1; J. Chem. SOC.,Perkin Trans. I, following paper. 8 H. Meier and K.-P. Zeller, Angew. Chem., Int. Ed. Engl., 1975, 14, 32. 9 Theoretical studies on this ring contraction have suggested that diradical intermediates may be involved, C. J. Moody, C. J. Pearson, and H.S. Rzepa, unpublished results. 10 H. Gunther, lsquo;NMR Spectroscopy,rsquo; Wiley, Chichester, 1980, p. 251. 1 1 E. C. Taylor, N. F. Haley, and R.J. Clemens, J.Am. Chem. SOC.,1981, 103, 7743. 12 E. Fahr, W. Fischer, A. Jung, L. Sauer, and A. Mannschreck, Tetrahedron Lett., 1967, 161. 13 J. Thiele, and A. Lachman, Liebigs Ann. Chem., 1895, 288, 267. 14 L. A. Carpino, A. A. Santilli, and R. W. Murray, J. Am. Chem. Soc., 1960, 82, 2728. Received 1 1th April 1986; Paper 617 12