J. CHEM. soc. PERKIN TRANS. 1 1991 223 Extension of the Aza-di-x-methane Reaction to Stable Derivatives. Photochemical Cycl ization of ply-Unsaturated Oxime Acetates Diego Armesto,a-* William M. Horspool,b**Fernando Langab and Ana Ramosb a Departamento de Quimica Organica, Facultad de Ciencias Quimicas, Universidad Complutense, 28040-Ma drid, Spain Department of Chemistry, The University, Dundee, DO I 4HN, Scotland, UK The successful sensitized photochemical conversion of oxime acetates of some P,y-unsaturated aldehydes and of one ketone into cyclopropane derivatives by the aza-di-n-methane (ADPM) rearrangement has been carried out. Thus, for example, the acetophenone-sensitized irradiation of the oxime acetate of 2,2-dimethyl-4,4-diphenylbut-3-enal affords the oxime acetate of 2,2-dimethyl-3,3-diphenylcyclopropanecarboxaldehyde in 86% yield and with a quantum yield of 0.12.The first report of the successful ADPM rearrangement with all-alkyl substitution is described. The photochemistry of molecules containing the imine group has been a subject of study for many years.',2 In recent years we have been interested in the effect of the incorporation of an imine group on the photochemical reactivity of organic molecules and we have observed the novel photoreactions of imines 1,3 z4 and 3.' It is clear from these results that the /.Sensitizedincorporation of a nitrogen into the system has a profound effect I on the course of the reaction and the behaviour of these Me Me I I molecules is substantially different from the reactions of the all- carbon analogues.The discovery of the photochemical reaction in which imines from P,y-unsaturated aldehydes 4 rearrange via the ADPM process to yield the cyclic imines 5 is of t Iimp~rtance.~.~Our previous studies on the ADPM reaction had shown that the efficiency of the cyclization was dependent on Me Me\ MeMe the nature of the substituent on the nitrogen Thus with an electron withdrawing group in the N-aryl imines 4a the Phquantum yield for product formation increased by a factor of ph% four from the unsubstituted compound (4a; R' = Ph).* This N,Rchange in reactivity was substantiated further in a study of N-Scheme 1 Ph material. Thus for the success of the ADPM rearrangement this electron transfer step has to be minimised.Attempts made by us and others lo to extend the reaction to more stable derivatives of aldehydes and ketones such as the oximes and oxime ethers failed. We reasoned that in these 1 2 3 derivatives the oxime and oxime ether groups had low ionization potentials which would lead to facile electron transfer and low efficiency of cyclization, if any took place. Thus, the aim of the current research was to find a stable derivative of P,y-unsaturated aldehydes or ketones which would complement the earlier study and provide a system which did not require special precautions to prevent hydrolysis. The present report 4 5 details the use of oxime acetate derivatives, one example of 4a = 5a; R' = Ar, R2= Me which was published in preliminary form,' and the 4b = 5b; R' = CH2Ar, R2= Me determination of quantum yields for two of the oxime acetates.benzylimines 4b.' In both of these studies an excellent linear correlation was obtained between log and the r+ substituent Results and Discussion constants. Based on these results we interpreted the mechanism The oximes 6 and the corresponding acetates 7 were readily of the cyclization as that shown in Scheme 1. The route to prepared from the aldehydes or ketones 8 by conventional product involves the conventional di-n-methane bridging methods in yields 70%. The identity of these compounds was mechanism. However, the alternative reaction mode of the readily proven by standard spectroscopic techniques.In our excited state is intramolecular electron transfer from the imine previous studies of the ADPM reaction acetophenone-sensitiz- nitrogen lone pair to the alkene moiety. This electron transfer ation had been shown to be effective and these conditions were process is energy wasting and results in decay back to starting used for the irradiation of the oxime acetate 7a in a conventional J. CHEM. SOC. PERKIN TRANS. 1 1991 6; R4= H 7; R4 = COMe 6a = 7a; R’ = Ph, R2 = Me, R3 = H 6b = 7b;R’ = R2 = Ph, R3= H 6c = 7c; R’ = Ph, R2 = R3 = Me 6d = 7d; R’ = Ph, R2= Me, R3 = Ph 6e =7e; R’ = R2 = Me, R3 = H 6f = 7f; R’ = R2 = R3 = Me 8 9 8a = 9a; R’ = Ph, R2 = Me, R3 = H 8b = 9b;R’ = R2= Ph, R3 = H 8c = 9c; R’ = Ph, R2= R3 = Me 8d; R’ = R3= Ph, R2 = Me 8e= 9e;R’ = R2= Me, R3 = H 8f ;R’ = R2= R3= Me PPh h KR 0 10a; R = H lob: R = Me immersion well apparatus.After irradiation for 30 min the solvent was removed under reduced pressure at low temperature. The resultant mixture was separated by flash column chromatography to afford acetophenone, starting material (1 1%) and a new product in 86% yield. This compound had retained the acetate group and exhibited an absorption at 1765 cm-’. The ‘H NMR spectrum showed that the absorption at 6 5.90 for the vinyl hydrogen of the starting material had disappeared indicating that a major change in the molecule had taken place and new absorptions had appeared in the 6 2-2.5 region. From previous with the imines of aldehyde 8a it was clear that this product was a cyclopropyl derivative, namely the oxime acetate 9a.Final proof for the structure was obtained by hydrolysis in EtOH-NaHSO, where the aldehyde 10a was obtained in good yield. The separation of the reaction mixture using column chromatography on silica gel is an improvement on the method described previously in which the acetophenone was removed by distillation under reduced pressure. Using that method we observed the formation of the corresponding nitrile 11 produced by thermal elimination of acetic acid from the cyclopropyl oxime acetate. This thermal elimination was totally suppressed by the new procedure described herein. The success of this ADPM reaction mode was further demonstrated by the photochemical conversion of the oxime acetates 7b and 7c into the corresponding cyclopropane derivatives 9b and 9c in 90% and 18% yield respectively.From these results it can be seen that the aldoxime acetates 7a and 7b are more reactive than the ketoxime acetate 7c and this is further substantiated by the failure of oxime acetate 7d to afford a cyclized product after 20 h irradiation. Changing the substitution on the terminal carbon of the azadiene system to methyl groups in oxime acetate 7e does not alter the reaction path and using acetophenone as sensitizer the cyclopropane 9e was obtained in 12% yield. This, however, was not the major product of the reaction and a second product, obtained in 57% yield, was identified as the oxetane 12 formed by the addition of the acetophenone in its triplet state to the alkene moiety of the oxime acetate 7e.The identity of the oxetane 12 was established by the usual spectroscopic techniques and microanalysis. The only regioisomer formed is in accord with the accepted mechanistic path for the formation of oxetanes.’ Previously we have suggested * that the aza-di-n- methane process was brought about by the excitation of the alkene moiety. It was clear from the result with acetophenone and oxime acetate 7e that there is an energy mismatch between the sensitizer and the alkene leading to the formation of the oxetane as the major product. This difficulty was overcome by using acetone as sensitizer whereby 7e gave the cyclopropane 9e in 32%.No oxetane was obtained from this reaction. The success of the ADPM rearrangement of this all-alkyl substituted oxime acetate 7e is of considerable importance. A similar reaction has not been reported in the oxa-di-n-methane reaction l3 and there is only one example in the di-n-methane system reported by Baeckstrom14 and by Bullivant and Pattenden.” The synthetic value of this cannot be stressed too much since the extension of this process to differently substituted oxime acetates will allow the ready synthesis of naturally occuring compounds or compounds of commercial value such as pyrethroid insecticides.’ The other oxime acetate 7f was unreactive under acetophenone sensitization and this is further conformation that the ketoxime acetates are less reactive in qualitative terms.These results substantiate our original proposal that the use of oxime acetate derivatives will suppress the adverse electron transfer from nitrogen to the alkene and permit the ADPM rearrangement of these derivatives of P,y-unsaturated alde- hydes. Steric factors do influence the reactivity as is seen by the sluggish behaviour of the ketoxime acetates. The photochemistry of the carbonyl compounds (8a4, f) has been studied l3 before and the usual reactivity found on sensitized irradiation is 1,3-acyl migration or decarbonylation. We have demonstrated that decarbonylation is also the fate of acetone- sensitized irradiation of 8e when the diene 14 is obtained in 32% yield. Further confirmation of the value of using oxime acetate derivatives was obtained from quantum yield measurements.These were measured for the photocyclization of the acetates 7a Me Me Phx Ph Ph CN 11 12 MePh Ph MeHMePh Me Ph Me 13 14 J. CHEM. SOC. PERKIN TRANS. 1 1991 and 7b and are made on conversions ranging from 4.9to 24.7% with four determinations for each compound. The results were plotted and extrapolated to zero time to give the optimum quantum yield in each case and details are recorded in the Experimental section. The results from the quantitative work show that the quantum efficiency for the formation of 9a from the oxime acetate 7a by acetophenone sensitization is 0.12 which is 13 fold better than the quantum yield for the cyclization of the imine (4a; Ar = Ph) to the corresponding cyclopropane 5a.8 The ADPM reaction can, in fact, be extremely efficient as shown by the cyclization of oxime acetate 7b which yields the corresponding cyclopropane 9b with a quantum yield of 0.82.The high efficiency of this reaction could be due to the diphenyl substitution of the central carbon. Zimmerman et al.17 have also observed similar changes in the di-n-methane reaction of 13 where the quantum yield of cyclization was measured as 0.42for the sensitized reaction. These results show that in some cases the aza-di-n-methane reaction is more efficient than the di-n-methane counterpart. The reason for the low reactivity of the ketoxime acetate 7c yielding the cyclopropane 9c and the failure of the derivative 7f to rearrange is unclear.However, Zimmerman et a1.18 have shown that substituents on the C-2 and C-4 positions of the 1,4-diene system suppress the di-x-methane rearrangement. This is interpreted as a steric effect. In our examples steric factors could also be responsible for the lowering of the efficiency of the ADPM rearrangement. Steric factors may be responsible for the failure of the cyclization of derivative 7d. In this case, however, an alternative deactivating mechanism involving the interaction of the phenyl group on C-1 with the C=N of the oxime acetate resulting in a decrease in the ionization potential of the oxime acetate group could be operative. Under these conditions the adverse electron transfer, discussed earlier, would become operative and suppress the cyclization. This study has shown that the ADPM rearrangement can be carried out using the stable oxime acetate derivative of unsaturated ketones and aldehydes. In addition to the stability of the derivatives another advantage is that the efficiency of the transformation to the cyclopropane derivatives is greatly enhanced and in some cases is greater than the efficiency re- ported for the di-n-methane rearrangement.The demonstration that the ADPM reaction can be carried out on substrates with only alkyl substituents increases greatly the synthetic potential of this rearrangement. It is interesting to note that the ADPM rearrangement provides a method to overcome the failure of P,y-unsaturated aldehydes and some ketones to undergo the oxa-di-n-methane process'3 by the simple method of converting them into the corresponding stable oxime acetates followed by sensitized irradiation and hydrolysis of the resultant cyclopropane derivative.Experimental M.p.s were determined on a Buchi 510D apparatus in open capillaries and are uncorrected. IR spectra were recorded on a Perkin-Elmer 257 spectrophotometer and band positions are reported in wavenumbers. NMR spectra were recorded on a Varian T-60A, Bruker WM-250or a Bruker 300 spectrometer with chemical shifts 6 expressed in ppm downfield from internal Me,Si and coupling constants J are given in Hz. UV-visible spectra were recorded in methylene dichloride solution using a Perkin-Elmer 550 spectrometer.The mass spectra were run by Dr. P. Bladon at the University of Strathclyde, Glasgow, UK, using an AEI (Kratos) MS 9 mass spectrometer fitted with a Mass Spectrometry Services Solid State Console and a GEC 905computer. Standard Procedure for Synthesis of 0ximes.-The oximes were prepared by refluxing the corresponding carbonyl compound with equimolecular amounts of hydroxylamine hydrochloride and pyridine (1 cm3) in ethanol (30cm3) for 1.5h for aldehydes and for 2.5 h for ketones. After conventional work up the oximes were isolated and purified by chromatography on silica gel and/or crystallization. 2,2-Dimethyl-4,4-diphenylbut-3-enaloxime 6a. From 8a ' as previously de~cribed.~ The I3C NMR spectrum of 6a showed the following signals: Gc(CDC1,) 27.4, 39.2, 127.0, 127.1, 127.3, 127.9, 128.1, 130.1,134.7, 139.3, 141.9, 142.9 and 157.2.2,2,4,4-Tetraphenylbut-3-enaloxime 6b. From 8b l7 (710mg, 1.9mmol). This gave 6b (610mg, 83%) as white crystals, m.p. 174-175 "C (from EtOH); v,,,(Nujol)/cm-' 3300, 1600 and 1580;6,(CDC13) 6.8(1 H, s, vinyl), 6.9-7.3 (20 H, m, ArH), 7.4 (1 H, s, HC=N) and 7.8(1 H, s, NOH); Gc(CDC1,) 56.1, 126.7, 127.0, 127.2, 127.4, 127.9, 128.1, 129.0, 129.8, 133.5,143.5, 144.3 and 155.7; m/z 389 (M', 1273,373 (27), 372 (loo), 345 (18), 344 (55), 267 (32), 191 (33), 167 (76), 165 (48) and 51 (31) (Found: M', 389.1802.C28H,,NO requires Mf, 389.1780). 3,3-Dimethyl-5,5-diphenylpent-4-en-2-oneoxime 6c.From ketone 8cI9 (2.18g, 8.3mmol). This gave 6c (2.02g, 88%) as white crystals, m.p. 8688 "C (from hexane); v,,,(KBr)/cm-' 3350 and 1620G,(CDCl,) 1.2 (6 H, s, CMe,), 1.7(3 H, s, CH,), 6.0 (1 H, s, vinyl) and 7.1-7.3(11 H, m, ArH and NOH); Gc(CDC13) 11.8, 27.4, 43.2, 127.0, 127.0, 127.1, 127.6, 127.9, 130.0,135.2,141.9,143.6and 162.5; m/z 279 (M', 38%), 264 (19), 263 (19), 262 (loo), 167 (14),91 (ll), 77 (7) and 51 (12)(Found: M+,279.1595.C,,H,,NO requires M', 279.1623). 2,2-Dimethyl-1-one oxime 6d. From1,4,4-triphenylbut-3-en-ketone 8d 2o (1 g, 3 mmol). This gave 6d (848mg, 81%) as a white crystalline solid, m.p. 134-1 36 "C (from EtOH); v,,,(KBr)/cm-' 3230, 1595 and 1570;6,(CDCl,) 1.1 (6H, s, CMe,), 6.1(1 H, s, vinyl) and 6.9-7.4 (16 H, m, ArH and NOH); G,(CDCl,) 27.7, 43.6, 126.9, 127.0, 127.0, 127.7, 127.9, 128.0, 128.0, 128.1, 129.9, 133.6, 134.4, 139.8, 141.7, 143.3 and 170.0; m/z 341 (M+, loo%),324 (96), 221 (9), 205 (12), 197 (lo), 191 (lo), 167 (31), 143 (16), 131 (97), 103 (25), 91 (59, 77 (30) and 51 (13) (Found: M', 341.1779.C2,H,,N0 requires M+, 341.1774). 2,2,4-Trimethylpent-3-enaloxime 6e.From 8e 21 (2.7g, 21 mmol). This gave 6e (2.51g, 85%) as white crystals, m.p. 43-45 "C (from hexane); vmaX(KBr)/cm-' 3300, 1640 and 1600; 6,(CDCl3) 1.2(6 H, s, CMe,), 1.6(3 H, d, J2,Me-C=C), 1.7(3 H,d,J2,MeC~),5.1(1H,m,vinyl),7.4(1H,s,HC=N)and8.1 (1 H, br s, NOH); Gc(CDC13) 18.6, 27.1, 37.6, 129.8, 134.7 and 158.6; m/z 141 (Mf, 473,127 (loo), 109 (14), 97 (72), 71 (6), 59 (15), 43 (37) and 41 (17) (Found: M+, 141.1153.C8HI5NO requires M+, 141.1 150).3,3,5-Trimethylhex-4-en-2-oneoxime 6f. From 8f 22 (1.51 g, 11 mmol). This gave 6f (1.27g, 76%) as a white crystalline solid, m.p. 59-61 "C (from EtOH-H20); v,,,(Nujol/cm-' 3290 and 1660;8,(CDCl3) 1.2 (6 H, s, CMe,), 1.6(3 H, d, J 2,MeC=C), 1.7(3 H,d, J 2, MeGC), 1.8 (3 H, s, MeC=N), 5.1(1 H, br m, vinyl) and 7.1 (1 H, br s, NOH); Gc(CDC1,) 11.6, 17.6, 26.7, 27.2, 41.5, 130.5,134.0and 163.5; m/z 155 (M', 19%), 140 (loo), 138 (20), 122 (ll), 96 (19), 69 (ll), 55 (33), 42 (18) and 41 (28) (Found: Mf, 155.1338.C9Hl,N0 requires M', 155.1310). Standard Method for the Synthesis of Oxime Acetates.- Acetyl chloride was added dropwise to a solution of the oxime in pyridine (2cm3) at 0 "C.The mixture was stirred for 1 h at room temperature, poured into sulphuric acid (10%) and extracted with diethyl ether. The organic layer was washed with a saturated solution of NaHCO, and water, and dried over MgS04. The desiccant was filtered off and the solvent removed by evaporation under reduced pressure. The product was purified by either crystallization or column J. CHEM. SOC. PERKIN TRANS. 1 1991 chromatography on silica gel using hexanediethyl ether (9:1) as eluent. l-Acetoxy-3,3-dimethyl-5,5-diphenyl-l-azapenta-1,4-diene7a. From 6a (1.10g, 4 mmol). This gave 7a (1.21g, 95%) as white crystals, m.p. 82-84 "C (from hexane); vmax(KBr)/cm-' 1760 and 1625;GH(CDCl3)1.3 (6 €3, s, CMe,) 1.9(3 H, s, MeCOO), 5.9 (1 H, s, vinyl) and 7.0-7.3(11 H, m, ArH and HC=N); Gc(CDC13) 19.6, 27.3, 39.9, 127.0, 127.4, 128.2, 128.9, 129.1, 130.3, 130.5, 139.0, 141.9, 142.4, 163.4 and 168.7; h,,,(CH,Cl,)/nm 248 (E 12 300dm3 mol-' cm-'); m/z 307 (Mf, lo%), 248 (loo), 232 (28), 205 (21), 165 (ll), 129 (8), 91 (19), 77 (6)and 51 (8) (Found: Mi, 307.1572.C20H21N02requires M+, 307.1577).l-Acetoxy-3,3,5,5-tetraphenyl-l-azapenta-l,4-diene7b. From 6b (700 mg, 1.8mmol). This gave 7b (600 mg, 77%) as white crystals, m.p. 116-1 17"C (from EtOH); v,,,(KBr)/cm-' 1750; GH(CDC13)2.0(3 H, s, MeCOO), 6.8(1 H, s, vinyl), 7.S7.3 (20 H, m, ArH) and 7.6(1 H, s, HC=N); Gc(CDC1,) 19.6, 56.6, 127.1, 127.4, 127.6, 128.0, 128.2, 128.2, 129.1, 129.9, 132.4, 138.9, 142.8, 142.9, 162.3 and 169.0;h,,,(CH,Cl,)/nm 235 (E 13 700 dm3 mol-' cm-') and 251 (14 800);m/z 431 (M+,0.5%)373 (57), 372 (98), 371 (loo), 344 (60), 294 (33), 293 (28), 267 (30), 265 (26), 216 (28), 191 (19), 178 (40), 167 (84), 152 (16) and 43 (22) (Found: M+,431.1885.C30H2,N02 requires M+, 431.1885).1-Acetoxy-2,3,3-trimethyl-5,5-diphenyl-1,4-diene1 -azapenta-7c. From 6c (1.93g, 7 mmol). This gave 7c (1.7g, 77%) as a colourless oil after flash chromatography; v,,,(KBr)/cm-' 1760 and 1630;GH(CDC13)1.3 (6H, s, CMe,), 1.7(3 H, s, CH,C=N), 2.1 (3 H, s, MeCOO), 6.0(1 H, s, vinyl) and 7.0-7.7(10H, m, ArH); Gc(CDCI3) 13.7, 19.4, 27.3, 43.5, 126.8, 126.9, 127.3, 127.7, 129.8, 134.0,138.3, 142.1, 142.9, 168.5 and 169.2; h,,,(CH,Cl,)/nm 227 (E 34 800 dm3 mol-' cm-'), 253 (28 700) and 257 (24700); m/z 321 (M', 13%), 264 (12), 263 (54), 262 (loo), 220 (60), 205 (30),194(33), 179(13), 167(30), 143 (17), 105 (12), 91 (29) and 77 (14) (Found: M+, 321.1750.C21H23N02 requires M+, 321.1729).1 -Acetoxy-3,3-dimethy1-2,5,5-triphenyl-1,4-diene1-azapenta-7d. From 6d (600mg, 1.76mmol).This gave 7d (531 mg, 79%) as white crystals, m.p. 109-111 "C (from EtOH); v,,,(KBr)/cm-' 1710 and 1610;GH(CDCl3)1.2 (6 H, s, C(Me,), 1.9(3 H, s, MeCOO), 6.1 (1 H, s, vinyl) and 6.9-7.5(15 H, m, ArH); Gc(CDC13) 19.4, 27.3, 44.3, 126.8, 126.9, 127.0, 127.5, 127.6, 127.9, 128.2, 129.6, 133.0,139.3, 142.4, 143.1, 168.9 and 172.4; h,,,(CH,Cl,)/nm 253 (E 13 600 dm3 mol-' cm-') and 237 (12 600); m/z 383 (M+, 1%), 324 (67), 282 (12), 221 (8), 205 (ll), 165 (lo), 143 (16), 131 (loo), 105 (11), 103 (38), 91 (46), 77 (12) and 43 (30) (Found: M+, 383.1885.C26H25N02requires M+, 383.1879).l-Acetoxy-3,3,5-trimethyl-1-azahexa-1,4-diene7e. from 6e (1 g, 7 mmol). This gave 7e (947 mg, 73%) as a colourless liquid after flash chromatography; vmax(liq. film)/cm-' 1770 and 1625; GH(CDC13)1.3 (6 H, s, CMe,), 1.6(3 H, d, J 2, CH3C=C), 1.7(3 H, d, J 2, Mew), 2.2(3 H, s, MeCOO), 5.1 (1 H, m, vinyl) and 7.6(1 H, s, HC=N); Gc(CDC13) 13.7, 19.3, 26.7, 28.4, 73.9, 128.7, 135.4, 164.9 and 168.6;h,,,(CH,Cl,)/nm 228 (E 10300 dm3 mol-' cm-'); m/z 182 (M+, 373,126 (59), 108 (28), 97 (loo), 71(lo), 55 (32), 43 (44) and 41 (29) (Found: M+, 183.1259.CloHl,NO, requires M+, 183.1255). l-Acetoxy-2,3,3,5-tetramethyl-7f. From l-azahexa-174-diene 6f (1.23g, 8 mmol). This gave 7f (1.10g, 71%) after flash chromatography as a colourless oil; v,,,(KBr)/cm-' 1760 and 1630;GH(CDC13)1.3(6H, s, CMe,), 1.6(3 H, d, J2,MeC=C), 1.7 (3 H, d, J2,MeC=C), 1.9(3 H, s, MeCOO), 2.1(3 H, s, MeC=N) and 5.1 (1 H, m, vinyl); Gc(CDC13) 13.3, 17.4, 19.4, 26.3, 26.9, 42.0, 129.5, 134.6,168.9 and 171.9;h,,,(CH,Cl,)/nm 228 (E 8500 dm3 mol-1 cm-'); m/z 197 (M+, 873, 182 (53), 140 (loo), 138 (40),97 (19), 96 (33), 51 (14), 43 (32) and 41 (6) (Found: M+, 197.1386C1 1H19N02 requires M+, 197.1416). Preparative Photolysis of Oxime Acetates 7a-f.-Preparative photolyses were carried out in an immersion-well apparatus with a Pyrex filter and a 400 W medium pressure Hg arc lamp.Solutions of the oxime acetates in the solvent indicated in each case were purged for 1 h with deoxygenated nitrogen and irradiated under a positive pressure of nitrogen. After completion of the irradiation the solvent was removed under reduced pressure, and the products were separated by chromatography on silica gel using mixtures of hexanediethyl ether as eluent. Irradiation of 7a. (a)Acetophenone as sensitizer. Compound 7a (400mg, 1.3 mmol) and acetophenone (2g) in benzene (330 cm3) were irradiated for 30 min. Chromatography of the crude photolysate using hexane4iethyl ether (9:1) afforded: aceto- phenone (1.96 g), starting material (46 mg, 11%) and cyclopropane9a (344mg, 8673,m.p.130-132"C (from hexane); v,,,(KBr)/cm-' 1765 and 1610;GH(CDC13)1.1 (3 H, s, Me), 1.3 (3 H, s, Me), 2.1 (3 H, s, MeCOO), 2.5(1 H, d, J 10,CH) and 6.9-7.4(1 1 H, m, ArH and HC=N); Gc(CDC1,) 19.4, 20.7, 25.3, 29.7, 33.2, 48.2, 126.5, 126.7, 128.5, 128.7, 130.5, 140.3, 143.6, 159.7and 168.5; m/z 307 (Mf, 273,265 (14), 248 (loo), 232 (48), 220 (27), 206 (33), 191 (18), 165 (59), 154 (21), 91 (17), 60 (20) and 43 (47) (Found: M+, 307.1572.C,,H,,NO, requires Mi, 307.1577);when acetophenone was removed from the crude photolysate by distillation nitrile 11 was obtained in 11% yield, m.p. 124-125 "C (from hexane); v,,,(KBr)/cm-' 2230; GH(CDC13)1.1 (3 H, S, Me), 1.4(3 H, S, Me), 2.1(1 H, S, CH) and 7.2-7.5(10H, m, ArH); Gc(CDC13) 21.8, 22.1, 24.1, 29.8, 47.7, 119.2, 127.0, 127.3, 128.6, 128.8, 128.9, 129.8, 139.1 and 141.9; m/z 247 (Mi, 77%) 232 (94), 220 (38), 205 (ll), 165 (loo),154 (47), 128 (5), 91 (lo), 77 (12) and 51 (14) (Found: M', 247.1361.C18H17N requires M+, 247.1357)and the cyclo-propane 9a in 79% yield.(b)Acetone as sensitizer.Compound 7a (500 mg, 1.6mmol) in anhydrous acetone (280 cm3) was irradiated for 3 h. Flash chromatography of the crude photolysate afforded starting material (225mg, 45%) and cyclopropane9a (175mg, 35%). Irradiation of 7b. Compound 7b (294 mg, 0.68mmol), and acetophenone, (2g) in benzene (350 cm3) were irradiated for 30 min. Chromatography of the crude photolysate using hexane- diethyl ether (9:1) afforded acetophenone (1.9 g), starting material (20mg, 7%) and cyclopropane 9b (264mg, 90%), m.p.161-162"C (from EtOH); v,,,(KBr)/cm-' 1645 and 1590; GH(CDC13)2.1 (3 H, s, Me), 3.9(1 H, d, J 10,CH) and 6.9-7.5 (21 H, m, ArH and HC=N); Gc(CDC13) 19.5, 31.9, 48.9, 126.2, 126.8, 127.9, 128.4, 129.2, 131.6, 139.5, 142.4, 160.6 and 168.5; m/z 431 (M+, 1%), 430 (4), 373 (72), 372 (loo), 371 (81), 370 (79, 345 (79), 344 (97), 294 (52), 167 (82), 166 (73), 165 (90), 77 (47) and 43 (64) (Found: M', 431.1882.C30H25N02requires M+, 43 1.1885). Irradiation of 7c. Compound 7c (670 mg, 2.1 mmol) and acetophenone (2 g) in benzene (280cm3) were irradiated for 20h. Chromatography of the crude photolysate using hexanediethyl ether (95:5)afforded starting material (380 mg, 57%) and cycfopropane9c (1 21 mg, 1873, m.p.153-1 54 "C (from hexane); v,,,(KBr)/cm-' 1720and 1620;GH(CDC1,) 1.1 (3 H, s, Me), 1.5 (3 H, s, Me), 1.9(3 H, s, MeCN), 2.0 (3 H, s, MeCOO), 2.4(1 H, s, CH) and 7.1-7.4(10H, m, ArH); GC(CDCl3) 14.9,18.1,20.4, 26.6,29.5,38.5,48.1,125.7,128.0,128.4,130.0,130.4,140.2,144.4, 163.4and 170.4; m/z 321 (M', 2%), 279 (12), 263 (62), 262 (loo),220 (33), 205 (59), 165 (21), 91 (20) and 77 (12) (Found: Mf, 321.1759.C21H23N02requires M+, 321.1729). Irradiation of 7d. Compound 7d (352 mg, 0.92mmol) and acetophenone (2.1g) in benzene (330 cm3) were irradiated for 20 h. After removing the acetophenone by distillation under reduced pressure only starting material was recovered. No evidence of any reaction was found.Irradiation of 7e. (a)Acetophenone as sensitizer. Compound J. CHEM. SOC. PERKIN TRANS. 1 1991 Table 1 Summary of quantum yield data for the conversion of l-acetoxy-3,3-dimethyl-5,5-diphenyl-l-azapenta-l,4-diene7a into cyclo- propane 911 Run Acetate (mmol) Light input (mE) Conversion (%I Photoproduct mmol) Quantum' yield 1 0.1925 0.0799 4.9 0.954 0.120 2 0.1987 0.1569 9.8 1.95 0.124 3 0.1835 0.2425 13.9 2.55 0.105 4 0.2040 0.4475 24.7 5.04 0.113 ~~~ ~ Optimum quantum yield = 0.12. Table 2 Summary of quantum yield data for the conversion of l-acetoxy-3,3,-5,5-tetraphenyl-l-azapenta-l,4-diene7b into cyclopropane 9b Run Acetate (mmol) Light input (mE) Conversion (%I Photoproduct (1C2mmol) Quantum yield 1 0.1258 0.01 76 10.1 1.27 0.722 2 0.1445 0.0247 13.5 1.95 0.790 3 0.1394 0.0396 20.7 2.89 0.730 4 0.1459 0.0500 22.3 3.26 0.650 Optimum quantum yield = 0.82.7e (370 mg, 2 mmol) and acetophenone (1.8 g) in benzene (280 refluxed for 2.5 h affording nitrile 11 (12 mg, 1573, aldehyde 10a cm3) were irradiated for 2 h. The acetophenone was removed by (41 mg, 52%) and starting material (31 mg, 31%). distillation under reduced pressure at room temperature. Hydrolysis of 9c. Compound 9c (100 mg, 0.31 mmol) was Chromatography of the crude photolysate afforded starting refluxed for 15 h affording ketone 10b (47 mg, 57%) and starting material (100 mg, 27%), cyclopropane 9e (40 mg, 12%) as a material (39 mg, 39%). colourless oil; vmax(liq.film)/cm-' 1760 and 1610; GH(CDC13) 1.3 (6H,s,CMe,), 1.4(6H,s,CMe2),1.6(1H,d,Jl0,CH),2.3(3H,Quantum Yield Measurements.-Quantum yield determin- s, MeCO,) and 7.6 (1 H, d, J 10, CH=N); G,(CDCl,) 14.3, 17.0, 18.4, 22.2, 27.8, 32.3, 159.0 and 167.6; and the oxetane 12 (210 mg, 57%) as a colourless oil; vmax(liq. film)/cm-' 1760 and 1630; G,(CDCl,) 0.7 (3 H, s, Me), 1.1 (3 H, s, Me), 1.2 (6 H, s, CMe,), 1.6 (3 H, s, Me), 2.0(3 H, s, Me), 4.1 (1 H, s, CH) and 6.9- 7.1 (1 H, S, CH=N); G,-(CDC13) 19.3, 21.8, 23.6, 24.6, 25.7, 40.3, 45.4, 87.5, 90.7, 123.5, 126.2, 127.7, 144.6, 163.0 and 168.5; m/z 243 (M+ -AcOH, 1%), 184 (34), 183 (89), 169 (35), 168 (94), 146 (93), 122 (94), 121 (99), 108(77), 96 (86), 77 (69) and 43 (100).(b)Acetone as sensitizer. A solution of 7e (460 mg, 2.5 mmol) in acetone (330 cm3) was irradiated for 4 h. After removing the solvent, the crude photolysate was chromatographed using hexane-diethyl ether (9: 1) yielding starting material (193 mg, 42%) and cyclopropane 9e (147 mg, 32%). Irradiation qf7f. Compound 7f (400 mg, 2 mmol) in acetone (280 cm3) was irradiated for 20 h. After removing the solvent only unchanged 7f was recovered. No evidence of any reaction was found. Photolysis qf 8e. Aldehyde 8e (509 mg, 4 mmol) in acetone (330 cm3) was irradiated for 2 h. After the removal of the acetone by distillation (Vigreux column) the crude photolysate was chromatographed (pentane as eluent) affording starting material (53 mg, 10%) and diene 14 (124 mg, 32%) which was identified by comparison of spectroscopic data.23 General Procedure for Hydrolysis of Oxime Acetates.24- Sodium hydrogen sulphite (5 cm3, 45%) was added to a solution of the oxime acetate in EtOH (15 cm3) and the mixture was heated at reflux for variable times.The crude reaction mixture was extracted with diethyl ether, and the organic layer was washed with HCI (lo%), NaHC03 (10%) and water, and dried over MgSO,. The desiccant was filtered off, and the solvent evaporated under reduced pressure. The reaction products were separated by flash chromatography on silica gel. Hydrolysis of 9a. Compound 9a (100 mg, 0.32 mmol) was ations were carried out using a 200 W high pressure Hg arc lamp in conjunction with a Bausch and Lomb model 33-86-07 grating monochromator.Irradiations were carried out at 365 nm in benzene using acetophenone (2 g) as sensitizer. Potassium ferrioxalate actinometry 25 was used to measure light output in all the experiments. The conversion into products was determined using 'HNMR (300 MHz) of the crude photolysate with anisole as the internal standard. Solutions of the compound in anhydrous benzene (3 1.5 cm3) were irradiated in a cylindrical quartz cell to 4.9-24.7% conversion under an atmosphere of nitrogen. The solutions were purged with nitrogen for 30 min prior to irradiations. The results obtained are tabulated (Tables 1 and 2) below. Acknowledgements We thank the British Council and the Ministerio de Educacion y Ciencia of Spain for a Fleming Fellowship to two of us (F.L. and A. R.), the Direccion General de Investigacion Cientifica y Tecnica of Spain (Grant No. PB 89/0144), and NATO (Grant 1764/89) for financial assistance. References 1 A. C. Pratt, Chem. SOC. Rev., 1977,6,63;A. Padwa, Chem. Rev., 1977, 77, 37. 2 P. S.Mariano, Org. Photochem., 1987,9,1. 3 D.Armesto, W. M. Horspool, R. Perez-Ossorio and A. Ramos, J. Chem. SOC., Perkin Trans. 1, 1986,96. 4 D. Armesto, M. G. Gallego, R. Perez-Ossorio and W. M. Horspool, Tetrahedron Lett., 1983,24, 1089;J. Chern. SOC., Perkin Trans. 1, 1986,799. 5 D.Armesto, M. J. Ortiz, R. Perez-Ossorio and W. M. Horspool, Tetrahedron Lett., 1983, 24, 1197; J. Chem. SOC., Perkin Trans. 1, 1986,623. 6 D.Armesto, J. A. F. Martin, R. Perez-Ossorio and W. M. Horspool, Tetrahedron Lett., 1982, 23, 2149; J. Chem. Res., 1986, (S),46; (M),631. 7 D. Armesto, F. Langa, J. A. F. Martin, R. Perez-Ossorio and W. M. Horspool, J. Chem. Soc., Perkin Trans. 1, 1987,743. 8 D. Armesto, W. M. Horspool, F. Langa and R. Perez-Ossorio, J. Chem. SOC., Perkin Trans. 2, 1987,1039. 9 D. Armesto, W. M. Horspool and F. Langa, J. Chem. SOC., Perkin Trans. 2, 1989,903. 10 A. C. Pratt and Q. Abdul-Majid, J. Chem. SOC., Perkin Trans. 1,1987, 359. 11 D. Armesto, W. M. Horspool and F. Langa, J. Chem. SOC.,Chem. Commun., 1987,1874. 12 H. A. J. Carless, in Synthetic Organic Photochemistry, ed. W. M. Horspool, Plenum Press, New York, 1984, p. 425. 13 K. N. Houk, Chem. Rev., 1976,76,1. 14 P. Baeckstrom, Tetrahedron, 1978, 34, 3331; J. Chem. SOC., Chem. Commun., 1976,476. 15 M. J. Bullivant and G. Pattenden, J. Chem. SOC., Perkin Trans. 1, 1976,256; Pyrethrum Post, 1976,13,110 (Chem. Abstr., 1977,87,5 1 18). 16 K. Naumann, Chemie der Synthetischen Pyrethroid-Insektizide, in J. CHEM. SOC. PERKIN TRANS. 1 1991 Chemie and Planzenschutz- und Schadlings-bekampjiungsmittel,1981, Springer-Verlag, Berlin, Band 7. 17 H. E. Zimmerman, R. J. Boettcher and M. Braig, J. Am. Chem. Soc., 1973,95,2155. 18 H. E. Zimmerman and D. N. Schissel,J. Org. Chem., 1986,51, 196. 19 A. C. Pratt, J. Chem. Soc., Perkin Trans. 1, 1973,2496. 20 H. E. Zimmerman and A. A. Baum, J.Am. Chem. SOC., 1971,93,3646. 21 R. H. Rasek, R. D. Clark and J. H. Chaudet, J. Org. Chem., 1961,26, 3 130. 22 J. L. Dolby and C. L. Wilkins, Tetrahedron, 1969,2381. 23 A. Van der Weerdt and H. Cerfontain, J. Chem. SOC., Perkin Trans. 2, 1977, 1357. 24 S. H. Pines, J. M. Chemerda and M. A. Kozlowsky, J. Org. Chem., 1966, 31, 3446. 25 C. A. Parker and C. G. Hatchard, Proc. R. SOC.London, Ser. A, 1956, 235, 518. Paper 0/01957G Received 2nd May 1990 Accepted 13th August 1990
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