Formation of heterocyclic compounds by use ofNprime;-diphenylmethylene-N-phenyl-N-trimethylsilylurea

摘要

1976 1523Formation of Heterocyclic Compounds by Use of A/'-Diphenylmethylene-N- p hen yl -A/-t r i met hylsi lylu reaBy lsamu Matsuda," Sakae Yamamoto, and Yoshio Ishii, Department of Synthetic Chemistry, Faculty ofThe reactions of N'-diphenylmethylene-N-phenyl-~-trimethylsilylurea (I) with variety of acceptor molecules havebeen studied. Imidazolidinone, triazinone, and pyrimidinone derivatives were obtained via 4 + I or 4 + 21cyclizations with cyclohexyl isocyanide, methyl isocyanate, dimethyl acetylenedicarboxylate, and trichloroaceto-nitrite. followed by desilylation with methanol. Dimethylcyanamide reacts with the urea (I) to give 3-diphenyl-methylene-I ,I -dimethyl-2-phenylguanidine (VIII) via the thermal decomposition of the intermediate 1.4-di-hydro- Z-dimethylamino- 6-trimet hylsilyloxy-I .4.4- trip hen yl- 1,3,5 - triazine. Linear products of insertion in to asilicon-nitrogen bond of the urea (I) are obtained, possibly via a common intermediate, in the reactions withdiphenylketen and with chloral.2.3-Dihydro-6-methyl-2,2-diphenyl-3-phenylcarbamoyl-l,3-oxazin-4-one isformed from d i kete n (4- met h yle neoxetan - 2 -one) .Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464, Japan1,3,5-TRIAZINEDIONE derivatives have been obtained inthe reactions of N-trimethylsilyl- and N-trimethylstan-nyl-diphenylmethyleneamine with two equivalents ofisocyanate.lS2 The reaction was shown to proceed in astepwise fashion, i.e. with formation of a 1 : 1 insertionproduct (I) followed by reaction with another moleculeof isocyanate.The insertion product (I) is consideredto exist as an equilibrium of the urea (Ia) and the imidate(Ib), interconvertible through an intramolecular 1,3-migration of the t rimeth ylsilyl group .l, 3,PhzC=N-C -N-SiMe3 ,- PhZC=N-C=NPhI0--SiMe,ll I0 Ph(la) (Ib)A 4 + 11 or 4 + 21 cyclization reaction would beexpected from the interaction of compound (I) withdienophiles, involving the C=N-C=N linkage of the1 I. Matsuda, K. Itoh, and Y. Ishii, J.C.S. Perkirt I , 1972,a H. Suzuki, K. Itoh, I. Matsuda, and Y. Ishii, Bull. Chem.1678.SOC. Japan, 1974, 47, 3131.form (Ib). The present paper describes two types ofreaction of compound (I) with various acceptor moleculesto give heterocyclic compounds or linear insertionproducts, via a common intermediate.RESULTS AND DISCUSSION4 + 21 CycZizations.-The reaction of N'-diphenyl-methylene-N-plienyl-N-trimethylsilylurea (I) with 1equiv.of methyl isocyanate gave the triazinone (IIa) in89 yield, identified on the basis of the elementalanalysis and comparison of i.r. and n.m.r. spectra withthose of the 3-phenyl analogue (IIb).l Methanolysis ofthe product (Ira) gave the triazinedione (111) identicalwith an authentic sample.2Dimethyl acetylenedicarboxylate reacted with theurea (I) to give the pyrimidine (IVa) and its pyridonetautomer (IVb) in 35 yield. Methanolysis of theproduct gave the pyrimidinone (V) quantitatively. Theinterconversion between the tautomers (IVa) and (IVb)3 J.Pump and E. G. Rochow, Chem. B e y . , 1964, 97, 627.4 K. Itoh, M. Katsuda, and Y. Ishii, J . Chem. SOC. (B), 1970,3021524 J.C.S. Perkin IPh, ,Ph Ph, ,Ph electron-withdrawing substituent and the latter anelectron-donating one. A high temperature and a longtime (45 days at 105 ldquo;C) were necessary. No pureproduct was obtained in the reaction of trichloroaceto-nitrile, but methanolysis of the reaction mixture gave thetriazinone (VII) in 7 yield, identified by analysis andi.r. (vC=o 1679 cm-l) and U.V. spectra (no absorption atca. 250 nm, suggesting the absence of a Ph,C=N-C=Nlinkage). The reaction of dimethylcyanamide (28 days)gave the guanidine (VIII) and trimethylsilyl isocyanate.amp;. 0 R Hbsol;NF.N/Meil Y I Io,cbsol;,o Me3SiO/ ldquo;Nrdquo; bsol;OPh Ph(m) (Illa; R=Meb; R=Phwas observed by 1H n.m.r.spectroscopy at varioustemperatures. A set of three singlets at 7 10.02, 6.51,PhPcG/C4MeII II cbsol; 0cMe3SiOrsquo; Fh lsquo;C02MeMeO-C-CCC-C - OMePh Phbsol; /Me3Sibsol;N,C,C / CO2Mell0H0(IYb)SCEXEME 1RC-N+ lsquo; 6 H6Ph Ph, /NJLNII ilCbsol; 0C-RMe3SiO/ Fh( R = CCI31 r- Ph Ph, /H---N/C,NOH Ph ldquo;1,I I I c. 0cNPhP h 2 C = N -C @ (VIII 1ldquo;Me23.Me3 Si - N= C= 0SCHEME 2and 6.25 which appeared above room temperature areascribed to the Sillle, and the two C0,Me groups respec-tively. However the spectrum at -30 ldquo;C showed twosets of three singlets, at z 10.00, 6.55, and 6.24 andlsquo;t 10.13, 6.50, and 6.29 (intensity ratio 2 : 1). This canbe explained in terms of an intramolecular 1,3-migrationof the trimethylsilyl group, as reported for amides 394 andfor ~ r e a s .~A carbon-nitrogen triple bond is relatively unreactivein Diels-Alder reactions. However the reactions of theurea (I) with trichloroacetonitrile and with dimethyl-cyanamide, were investigated. The former has anI. Matsuda, K. Itoh, and Y . Ishii, J . Chem. Soc. (C), 1969,701.The former was identified by analysis (C,,H21N,,0.5-H,O) and the n.m.r. spectrum T 7.05 (6 H, s, NMe,), 5.55brPh Yc6 H6 I I:C=O + ( I ) - Ph2C=N-C-N-C-OSiMe3 I I I0 2Y Z v (1x1 Ph2C=(XI H CC13(1 H, s, OH), and 2.8-3.5 (15 H, 3 Ph). These reactionsare explained in terms of the intermediate (VI) derivedfrom 4 + 21 cyclization. The electron-donating di1976 1525methylamino-group lowers the stability of this inter-mediate, resulting in its decomposition in the latter case(Scheme 2).C-1 in the intermediate (XI), followed by N + 0migration of the trimethylsilyl group path (i).How-ever migration of the trimethylsilyl group from N to the0-(xn)IO-SiMe3( x m )SiMe,IPbC -+-C -NPhIIMeOH__cij( I 1( A = N o r C )A d C - 1path(i1 - Ph2Crsquo;II,f A=Bi6 Arsquo;bsol;C B0(XI 1II0(XSYIlsquo;PhPh( A =Ol 1Ph2C=N-C-N -6-A-SiMe3I10(XV)SCHEME 3The reaction of the urea (I) with 1 equiv. of diphenyl-keten proceeded smoothly even at room temperatureand the product (IX) was stable in moist air and toprotic solvents. It was identified by analysis and ix-,n.m.r., and U.V.spectra strong absorption due ton+ x* transition a t 258.5 nm (log E 4.66 in EtOH)characteristic of Ph,C=N-C=O .Chloral also reacted with the urea (I) to give the linearadduct (X), identified by analysis and spectral data.The carbon-oxygen double bonds in diphenylketen andchloral and the carbon-carbon double bond in diphenyl-keten can undergo 4 + 21 cyclization; however, onlylinear insertion products were obtained in the foregoingreactions. Thus there are two different types of reactionwith the urea (I), depending upon the character of thedienophile: (i) 4 + 21 cyclization, observed withmethyl isocyanate, dimethyl acetylenedicarboxylate,and trichloroacetonitrile ; and (ii) linear consecutiveinsertion, giving (IX) and (X), observed with diphenyl-keten and chloral (Scheme 3).Initial nucleophilicattack of the amino-nitrogen atom in (Ia) on a dienophilegives a zwitterionic intermediate (XI), and this is followedby the product-determining step. The heterocycle (XIII)is formed by the attack of the anionic terminal A- onanionic terminal A- may be preferred to the attack ofA- on C-1 when the terminal atom is oxygen (which has a,OSi MeN=C,D N = C + ( I 1 4 phbsol;Crsquo; NPhphrsquo; lsquo; c /=I= II f N I 4/SiMe (XVI)lsquo;N-C--N=CPh, k e O H@N=CI I!Ph 00H, //N-C cxvm 1Phkrsquo; ldquo;Ph/ lsquo;crsquo;Ph 11 d(xvn1526 J.C.S. Perkin IPh1Ph,C=N--C--N-C -CH2 ---MeH0H(xxm)0II0+ MeOH + MeMe3Si0Ph*C=N NjC/ 'PhI I0+Ph2C EN-C -N -- SiMe,II I0Ph, ,Ph 11Hbsol;N,c.c/CI I'HPh( XXY 1-Me(XXISiMe3 dII00 +MeOHPh' p'"p " l oo== c,Ph PH(XXII)+ MeOH t cyctizat ion !4 'N-SiMe,I'N -SiMe3IPh t Ph(XXIV)SCHEME 4strong affinity for a silicon atom 6), giving a linear quantitatively to give the imidazoline (XVI), whichinsertion product (XV) path (ii) .Semiempirical afforded the imidazolidinone (XVII) upon methanolysis.SCF-LCAO MO calculations (CND0/2) support such a Although a 1,l-insertion product (XVIII) might havestepwise product formation.' been expected in view of Lappert's result,8 it is excludedwith 1 equiv. of cyclohexyl isocyanide proceeded almost unpublished work.6 K. Itoh, T. Katsuura, I. Matsuda, and Y . Ishii, J . Organo-metallic Chew., 1972, 34, 63. 1967, 5, 225.E4 + '1 Cyczizations*-The reaction Of the urea ('17 H.Suzuki, H. Kate, 1. Matsuamp;, K. Itoh, and y. Isfii,M. F. Lappert and euro;3. Prolrai, Adv. Organometallic Chem.1976 1527by the n.m.r. spectrum and by the absence of a x ---t x*transition (at ca. 250 nm; Ph,C=N-GO) and the exis-tence of an exchangeable aniino-yroto11 ( s ca. 3.95; v , , ~3 280 cm-l) in the methanolysis product (XVII). Theformation of (XVI) can be explained in terms of a 4 + 11cyclization following path (i) in Scheme 3.Renctiott of the Urea (I) with Diketen.-Treatment ofthe urea (I) with 1 equiv. of diketen (4-methyleneoxetan-2-one) gave a brownish oil which showed two trimethyl-silyl groups (Z 9.92 and 9.91) in the n.m.r. spectrum. Itresembled the product of the reaction of LV-trimethylsilyl-(diphenylmethy1ene)amine with diketen, which gavethree isomeric 1 : 1 adducts, each of which was desilyl-ated to the same oxa~inone.~ Accordingly, the reactionmixture was desilylated with methanol directly, givingthe oxazinone (XXII) in good yield, identified fromanalysis and spectral data.Of the three other possiblestructures (SXII1)-(XXV), the linear structure (XXIII)was excluded because of the absence of a ~ + x ' ~transition (Ph,C=N-C=O) in the U.V. spectrum. Themethyl protons in structure (XXV) should resonate atT ca. 8.01deg; rather than at z 8.37 as observed. Anolefinic proton signal at T 5.17 also excludes structure(XXV). Structure (XXIV) is excluded by the absence ofO-H and C=N stretching vibrations in the i.r.spectrum;in fact N-H and G O stretching bands were observed, at3 230 and at 1734 and 1 673 cm-l, respectively. Thefirst step of the reaction is presumably nucleophilicattack of the amino-nitrogen atom in (I) on the carbonylatom to form a zwitterionic intermediate (XIX). Thismay be followed either by the formation of (XX), as aresult of ?3 _t 0 migration of thc trimethylsilyl group,or by direct cyclization to (XXI); the product (XXII)would be formed by desilylation of either precursor asshown in Scheme 4. In this reaction compound (I)plays the role of a dienophile in a different type of 4 + 21cyclization froin those recorded above. The reaction ofamp;met hyl-2,2-diphcnyl- 1,3-oxazin-4-one with phen ylisocyanate did not give the oxazinone (XXII), whichmeans that the presence of a trimethylsilyl group isnecessary for the synthesis of (XXII).EXPERIMENTALM.p.s were determined for samples in sealed tubes filledwith argon.1.r. spectra were recorded with a JASCOIR-403G and IR-S instruments. A JEOL C-60 HL instru-ment was utilized to record lH n.m.r. spectra, with tetra-methylsilane as internal standard. Mass spectra wereobtained with a JEOL JMS-O1SG spectrometer at anionizing voltage of 75 eV. A Hitachi 124 spectrophoto-meter was used for the measurement of U.V. spectra.N-Trimethylsilyl(diphenylmethy1ene) amine , N'-diphenyl-methylene-N-phenyl-N-trimethylsilylurea, diphenylketen,lland cyclohexyl isocyanide 1 2 were prepared according to theliterature. All reactions were carried out in an atmosphereof argon.Reactions of the Urea (I) with One Equivalent of Acceptor.-s H.Suzuki, I. Matsuda, K. Itoh, and Y. Ishii, Bull. Ckern.lo H. Toda, Yakzlgaku Zasshi, 1967, 87, 1351.SOC. Japan, 1974, 47, 2736.(a) Meethyl isocyanate. A mixture of the urea (I) (2.15 g,5.77 mmol), methyl isocyanate (0.336 g, 5.89 mmol), andbenzene (3 ml) was heated for 6 days a t 90-95 "C in asealed tube. The yellow oily product obtained by evapor-ation of volatile materials was recrystallized from benzene-n-hexane (1 : 7) to give white needles of 3,4-dihydro-3-methyl-lJ4,4-tri~henyZ-6-trimethyZsilyEoxy- 1,3,5-triuzin-2( 1H)-one (IIa) (89), m.p. 131-132 "C (Found: C, 70.1; H, 6.3.C2,H,,N,0,Si requires C, 69.9; H, 6.3), vmX.(CCl,) 1 698s(C:O) and 1 668s cm-1 (C:N), T (CDCI,) 9.88 (9 H, s, SiMe,),7.32 (3 H, s,NMe), and 2.7-3.1 (15 H, in, 3 Ph). Desilyl-ation with an excess of methanol gave 3-methyZ-1,4,4-tri-phenyZperhydro-lJ3,5-triazine-2,6-dione (111) quantitatively.White prisms were obtained by recrystallization frombenzene-n-hexane (2: 1) in 69 yield; m.p. 365-266 "C(Found: C, 73.8; H, 5.1; N, 11.7. C22H19N3O2 requires C,73.9; H, 5.4; N, 11.8), vmX. (KBr) 1730s and 1658scm-1 (C:O), 7 (CDCI,) 7.26 (3 H, s, NMe), 3.01br (1 euro;3, s,NH), and 2.7-3.1 (15 H, m, 3 Ph).A mixture of theurea (I) (2.35 g, 6.05 mmol) , dimethyl acetylenedicarboxyl-ate (0.835 g, 5.88 mmol), and benzene (3 ml) was heated for22 days a t 90-95 "C in a sealed tube. The oily residueobtained by evaporation was recrystallized from benzene-n-hexane (1 : 8) to give the pyrimidine diester (IV) as abrownish-yellow powder (0.74 g, 35) , m.p.148-149.5 "C(Found: C, 67.9; H, 5.8; N, 5.6. Calc. for C,9H,,N20,Si:C, 67.7; H, 5.9; N, 5.4), vmU. (ICBr) 1735s and 1680s(C:O) and 1 638s cm-1 (C:N), (CDCI,) 10.02br (9 H, s, SiMe,),6.51 (3H,s,OPuIe),6.25(3H,s,OMe),and2.5--3.0(15H,mJ3 Ph).Desilylation with an excess of methanol (3 nil) a t roomtemperature gave dimethyl 1,2,3,6-tetrahydro-2-oxo-3,6,6-tviphenyZ~yrinzidine-4,5-dicarboxyZate (V) as a white powder(89), m.p. 239-240 "C benzene-n-hexane (3 : l) (Found:C, 70.8; H, 5.2; N, 6.3. C,,H22N,0, requires C, 70.6;H, 5.0; N, 6.3y0), vmaX. (KBr) 1750s, 1 722s, and 1690scm-l (C:O) vne 442 (M+, 15x1, 411 (A!! - MeO, 4), 398(M - H - Hh-=C=O, 9), 383 (M - C02Me, 35), 366(M - Ph + H, 27), 365 (111 - Ph, loo), and 340 (amp;I -C0,Me - HNCO, 9), s (CDCI,) 6.62 (3 H, s, OMe), 6.57(3 H, s, OXfe), 3.88br (1 H, s, NH), and 2.5-4.1 (15 H, m,3 Ph).A mixture of the urea (I) (2.17 g,5.82 mmol), trichloroacetonitrile (1.34 g, 9.25 mmol), andbenzene (3 ml) was heated for 45 days a t 100-110 "C in asealed tube.Volatile materials were evaporated off underreduced pressure and the resulting oil, which was difficult topurify, was desilylated directly with an excess of methanol(5 ml). Evaporation, washing the residue with ether, andrecrystallization from benzene-n-hexane (2 : 1) gave 3,4-di-hydro- 1 , 4,4-tr~phnyl-6-trichloromethyl- 1,3,5-triazin-2 ( 1H)-oneas a yellow powder (VII) (4), m.p.220-221.5 "C (Found:C, 59.4; H, 3.7; N, 9.4. C22Hl,Cl,N,0 requires C, 59.4;H, 3.6; N, 9.5), v,= (KBr) 1679s (C:O) and 1640shcm-l (C:N) 7 (CDCl,) 2.7-3.2 (15 H, m, 3 Ph) and 1.82br(1 H, s, NH).(d) Dimethylcyanamide. A mixture of the urea (I)(2.05 g, 5.53 mmol), dimethylcyanamide (0.38 g, 5.38 mmol),and benzene (3 ml) was heated for 28 days a t 100-110 "Cin a sealed tube. Volatile materials were then evaporatedl1 E. C. Taylor, A. McKillop, and G. H. Hawks, Org. Syntk.,1972, 52, 36.l2 I. Ugi, R. Meyr, M. Lipinski, F. Bodesheim, and F. Rosen-dahl, Org. Synth., Coll. vol. V, 1973, p. 300.(b) Dimethy2 acetylenedicarboxylate.(c) Trichloroacetonitril1528off under reduced pressure.Trimethylsilyl isocyanate wasdetected in the volatile fraction by its i.r. (VN*=O, 2 260cm-l) and lH n.m.r. spectra T 9.74 (SiMe,). Recrystalliz-ation of the yellow oily residue gave white prisms of hydrated3-diphenylmethylene-1 , l-dimethyl-2-phenylguanidine (VIII) ,m.p. 76.5-78 "C from ethanol-n-hexane (4 : l) (72)(Found: C, 78.4; H, 6.7; N, 12.5. C,,H,,N3,0.5H,0 re-quires C, 78.5; H, 6.6; N, 12.5), vmx. (KBr) 1613m and1570cm-l (CX), T 7.05 (6 H, s, NM,), 5.55br (1 H, s, OH),and 2.7-3.4 (15 H, m, 3 Ph). Picric acid (0.044 g, 0.19mmol) was added to an ethanolic solution (4 ml) of thehydrated guanidine (VIII) (0.064 g , 0.19 mmol). Themixture was heated for 10 h under reflux. Evapor-ation, and recrystallization of the residue fromethanol-n-hexane (3 : 1) gave yellow prisms of the picrate(0.057 g, 60), m.p.263-265.5 "C (Found: C, 60.5; H, 4.1;N, 15.1. Cz2HzlN3,C6H,N,0, requires C, 60.4; H , 4.4;N, 15.1y0), vmx. (KBr) 1660s and 1630m cm-l (C:N).(e) Diphenylketen. When diphenylketen (0.35 g, 1.82mmol) was added dropwise to a solution of the urea (I)(0.74 g, 2.0 mmol) a t room temperature, an exothermicreaction ensued with change of colour from pale yellow t oorange. The mixture was stirred for 1 h a t room temper-ature and evaporated t o leave a yellowish orange residue.This was recrystallized twice from benzene-n-hexane (1 : 5)to give N'-diphenylmet~~ylene-N-(2,2-di~henyl-l-trimethyl-silyZoxyviny1)-N-PhenyZurea (IX) as a white powder (0.66 g ,70),m.p.152-153.5 "C (Found: C, 78.7; H, 5.9; N, 4.9.C,,H,,N,O,Si requires C, 78.4; H, 6.1 ; N, 4.9) , vmax. (KBr)1 656s (C:O) and 1 631s cm-l (CX), LX. (EtOH) 258.5 nm(log E 4.66) T 9.99 (9 H, s, SiMe,) and 2.6-3.5 (25 H , m, 5 Ph).A mixture of the urea (I) (2.57 g, 6.94 mmol),chloral (1.02 g, 6.90 mmol), and benzene (5 ml) was heatedfor 13 days a t 110 "C in a sealed tube. Evaporation,followed by recrystallization from cyclohexane, gave N'-diphenylmethylene-N-fihenyl-N- (2 , 2,2-trichloro- 1-trimethyl-sily1axyethyZ)ureca (X) (solvated) as a white powder (76),m.p. 81.5-84 "C (Found: C, 59.7; H, 5.8; N, 5.0. CZ5H,,-(f) Chloral.J.C.S. Perkin IC1,N202Si,0.5C,Hl, requires C, 59.9; H, 5.6; N, 5.1), vmx(KBr) 1 667s (C:O) and 1 637m cm-l (C:N) , (EtOH) 255.8nm (log E 4.01), T 9.77 (9 H, s, SiMe,), 8.59 (6 H, s, 3 CHJ,3.38 (1 H, s, CH), and 2.6-2.8 (16H, m, 3 Ph).(g) Cyclohexyl isocyanide. A mixture of the urea (I)(1.02 g, 2.75 mmol), cyclohexyl isocyanide (0.36 g, 3.0 mmol),and benzene (3 ml) was heated for 16 days a t 100-110 "Cin a sealed tube.Benzene was evaporated off to leave theimidazoline (XVI) (1.32 g, 96y0), vmx (CCl,) 1 730m (CO)and 1678s and 1653s cm-1 (C:N), T 9.78 (9 H, s, SiMe,),8.0-9.4 (11 H, m, cyclohexyl), and 2.3-3.0 (15 H , m, 3 Ph).Desilylation with an excess of methanol and recrystalliz-ation from benzene-n-hexane (2 : 1) gave 4-cycZo2iexy~imino-3,5,5-triphenyZimidazoEidin-2-one (XVII) (30) (Found :C, 79.4; H, 6.6; N, 10.3. C,,H,,N,O requires C, 79.2;H, 6.7; N, 10.3yo), m.p. 165-166 "C, v,,,. (KBr) 1720w(CO) and 1665s and 1 655sh cm-l (GIN), T 7.5-8.9 (11 H,ni, cyclohexyl), 4.91br (1 H, s, NH), and 2.8-3.2 (15 H, in,3 Ph), m/e 409 (A!!+, lo), 408 ( M - H, 20), 327 (M -cyclohexyl + H, loo), 326 (ill - cyclohexyl, 70), and 182(Ph,C=NH,+, 50).A mixture of the urea (I) (1.59 g, 4.28 mmol),diketen (0.38 g, 4.54 mmol), and benzene (3 ml) was heatedfor 3 days a t 120-130 "C in a sealed tube, then evaporatedunder reduced pressure ; the residue showed trimethylsilylproton resonances at T 9.92 and 9.91, suggesting a mixtureof isomers. The residue was desilylated with an excess ofmethanol (5 nil) ; recrystallisation of the product fromethanol gave 2,3-dihydro-6-met?ay1-2 , 2-d iphenyl- 3-plieny l-carbamoyZ-l,3-oxazin-4-one (XXII) as yellow needles (0.85 g,57), m.p. 271-273 "C (Found: C, 74.9; H, 5.4; N, 7.1.C24H,,N20, rcquires C, 75.0; H, 5.2; N, 7.3y0), v,,,. (KBr)1734s and 1 673s cm-l (CIO), 7 8.37 (3 H , s, CMe), 8.29br(1 H, s, NH), 5.17br (1 H, s, CH), and 2.6-3.2 (15 H, m,3 Ph), m/e 384 ( M + , 17), 265 (A4 - PhNCO, 22), 249(M - PhNCO - Me - H, 28), 207 (134 - PhNCO - Me -H - NCO, 49), and 180 (Ph,C=N', 100).5/2495 Received, 22nd December, 19757(h) Diketen