Photochemical delta;-hydrogen abstraction from acyclic and semicyclic monothioimides

摘要

J. CHEM. SOC. PERKIN TRANS. 1 1991 Photochemical amp;Hydrogen Abstraction from Acyclic and Semicyclic Monothioimides Masami Sakamoto," Masakazu Tohnishi, Tsutomu Fujita and Shoji Watanabe Department of Applied Chemistry, Faculty of Engineering, Chiba University Ya yoi- cho, Chiba 260, Japan Photochemical 6-hydrogen abstraction from acyclic and semicyclic monothioimides have been studied. Photolysis of acyclic monothioimides possessing a benzylic hydrogen atom at the amp;-position gave y-lactams, via a 1,5-diradical intermediate, accompanied by thioamides were generated by y-hydrogen abstraction. Irradiation of the five-membered semicyclic monothioimide, N-(3-p hen y Ipropio n y I) pyr ro Iidine-2-t h ion e, yieId ed 5 -mercapto-4-phen y I-1-azabic yc Io 3.3.01 oc t an-2-one.For N-(3-phenylbutyryl) pyrrolidine-2-thione, disproportionation, involving 1,6-hydrogen migration, was the main path. Photolysis of the six-membered semicyclic monothioimide, N-(3-phenylbutyryl)piperidine-2-thione, gave an unsaturated thiol, via a 1,4-hydrogen shift of a 1,5-diradical intermediate, accompanied by cyclisation product and piperidine-2-thione. Photochemical hydrogen abstraction from thioketones has Table 1 Photolysis of acyclic monothioimides la-lg been well studied.' P. de Mayo et al. reported that thioketones underwent photochemical hydrogen abstraction from the 6- Yield () ' position via x,x* singlet excited state (S,) and that this process was preferred to y-hydrogen abstraction.* Recently, the photo- 1 R' R2 R3 2 3 chemistry of nitrogen-containing thiocarbonyl compounds has received much attention from the mechanistic and synthetic view points. Since these compounds show somewhat different photochemical behaviour from that of carbonyl compounds, their photochemistry may also lead to useful syntheses of some heterocycle^.^ We have already reported that the photolysis of a b C d e f g Me Me0 Ph Ph Ph Ph Ph Me H H Me H H H Ph Ph Ph Ph P-MeOCbH, p-MeCbH, P-CICbH, 0 0 43 53 64 52 50 63 36 45 15 32 31 39 acyclic monothioimides led to hydrogen abstraction from the j3-position to produce thioketones via 2-mer~aptoaziridines.~ 'Isolated yield.Furthermore, irradiation of acyclic and semicyclic mono- thioimides gave j3-lactams by y-hydrogen abstraction from the thiocarbonyl moiety.' We now report a synthesis of y-thiocarbonyl group, the corresponding 5-mercaptopyrrolidin- lactams via amp;-hydrogen abstraction from acyclic and semicyclic 2-ones 2d-2g were obtained as shown in Table 1, irrespective of monothioimides.? the substituent on the thiobenzoyl ring.R'bsol;/R2 R2 SH Results and Discussion All monothioimides la-1 were easily prepared from acid chlorides and the corresponding thioamides in the presence of triethylamine. N-Isovalerylthiobenzanilidela was a red liquid Ph 0 whose UV spectrum exhibited maxima at 313 nm (E 8600) and 1 2 3 500 nm (E 160) derived from the n-m* region of the Scheme 1 Reaction conditions: hv, benzenethiocarbonyl group. When the acyclic monothioimide la was irradiated in benzene with a 1 kW high-pressure mercury lamp under argon until the starting material had disappeared, Irradiation of the semicyclic monothioimide lj gave the thiobenzanilide 3a was obtained in 63 yield.Photolysis of the bicyclic lactam 5-mercapto-4-phenyl- l-azabicyclo3.3.0octan-imide lb gave similar results. Irradiation of the monothioimide 2-one (2j-major SO, 2j-minor 3479, while 1-isovaleryl- and 1 -(3- 2c in methoxypropionyl)-pyrrolidine-2-thione1h and li were inert lc yielded 5-mercapto- 174,5-triphenylpyrrolidin-2-one 43 yield as a mixture of stereoisomers (major: minor 8:3) toward photolysis as shown in Scheme 2.$ The structure of accompanied by thiobenzanilide 3c (= 3a) (45) (Scheme 1). compound 2j was determined on the basis of elemental analyses The structure of y-lactam 2c was deduced from its spectra. The and spectral data.The 'H NMR spectrum of the major isomer IR spectrum (for solution in CHCI,) exhibited a carbonyl exhibited a peak at 6 1.52, assignable to the mercapto group frequency at 1700 cm-' characteristic of a five-membered (D,O-exchangeable), and three double doublets, which were lactam. The 'H NMR spectrum of the major isomer showed coupled to each other, at 6 2.69 (1 H,dd, J 15.5 and 6.9 Hz), 3.38 signals at 6 1.60 for SH (D,O-exchangeable) and three double (1 H, dd, J 15.5 and 12.8 Hz) and 3.74 (1 H, dd, J 12.8 and 6.9 doublets, coupled to each other, at 6 2.96 (1 H,dd, J 16.5 and 7.3 Hz), 3.27 (1 H, dd, J 16.5 and 9.5 Hz) and 4.04 (1 H, dd, J9.5 and 7.3 Hz).In the NMR spectrum, the peak derived from 7 We have already reported amp;-hydrogen abstraction from thioimide- like compounds N-acyl-and N-thioacyl-thioureas; H. Aoyama,the thiocarbonyl carbon did not appear, and new doublet and M. Sakamoto and Y. Omote, Chem. Lett., 1983, 1397. Another group singlet peaks were shown at 6c 55.3 (d) and 82.7 (s), assignable studies a similar reaction for cyclic thioimides; M. Machida, K. Oda,to C-4 and C-5, respectively. For other monothioimides Id-lg E. Yoshida and Y. Kanaoka, J. Org. Chem., 1985,50, 1681. which have a benzylic hydrogen atom at the amp;position to the 1Prolonged irradiation of the imides lh and li gave pyrrolidinethione. 348 J. CHEM. SOC. PERKIN TRANS. 1 1991 1h; R' = R2= Me li; R' = H, R2 = Me0 Ph 2j major 50 minor 34 0 0 lk 2k 38 4k 51 Ph MebMe 11 21 major 16 51 E 11 6 12 minor 11 Z 26 Scheme 2 Reaction conditions: hv, benzene Hz).In the 13C NMR spectra, the peak derived from the thiocarbonyl carbon did not appear and a new doublet and a singlet appeared at 6,54.5 (d) and 82.0 (s), assignable to C-4 and C-5, respectively. Mass spectra (SIMS) exhibited molecular-ion peaks at 234 (M + 1). For the imide lk, both of lactam 2k (38, one isomer was isolated) and 1-(3-phenylbut-3-enoyl)-pyrrolidine-2-thiol 4k (51) were obtained. The structute of compound 4k was determined on the basis of its spectral data. Furthermore, it was supported by the fact that desulphurisation by Raney nickel (W-3) gave amide 7,which was determined by comparison with an authentic sample prepared by acylation of pyrrolidine with 3-phenylbutyryl chloride as shown in Scheme 3.In the photolyses of the five-membered semicycilic imides lj and lk, pyrrolidinethione products were not detected at all. 4k -Ph 7 Scheme 3 Reagents and conditions: Raney nickel, MeOH When six-membered semicyclic monothiomides 11 was irradiated under the same conditions, a,P-unsaturated amide 1-(P-methylcinnamoyl)pyrrolidine-2-thiol(51-E11, 2 26) was obtained as the main product accompanied by bicyclic lactams 21 and 6, whereas photolysis of the imide 1k gave 1-(P,y-unsaturated alkanoyl)pyrrolidine-2-thiol4k (Scheme 2). For the formation of y-lactams 2c-2g and 2j-21, photo-chemical amp;hydrogen abstraction followed by cyclisation is * 1 cal = 4.184J s i amp;Enahstraction A4 1 8 2 yhydrogen abstraction 1.4-hydrogen 1.6-hydrogenR3R4 = 'cH214 shift S 51 4k il R3CNHR4 336 Scheme 4 Reagents and conditions: i, hv postulated as shown in Scheme 4.The intermediacy of diradical 8 was supported by the fact that disproportionation took place in the photoreaction of semicyclic monothioimides lk and 11, since it is reasonable that the unsaturated photoproducts 4k and 51, disproportionation products, are formed via diradical intermediate 8. 1,4-Hydrogen shift in diradical 8 affords n,P-unsaturated amide 51, whereas P,y-unsaturated amide 4k is formed oia 1,6-hydrogen shift.It seems that the difference in distance between the hydrogen atom and radical centre caused by the difference in conformation of the five-membered ring and that of the six-membered ring is reflected in the photoproducts. However, there is no satisfactory explanation at present. For the formation of thiolactams 3 and 6, a Type-11 cleavage (y-hydrogen abstraction) is postulated.' The UV spectrum of N-(3-phenylpropionyl)pyrrolidine-2-thione lj exhibited maxima derived from the n-m* band of the thiocarbonyl moiety at 426 nm (E 20). The photoreaction also proceeded when the imide lj was irradiated in the n+n* region (436 nm) selectively. The photocyclisation was sensitised by Michler's ketone (ET 62 kcal mol-')6** and thioxanthone (ET 65.5 kcal mol-').6 Though this photoreaction was not quenched by either (E)-stilbene (ET 50 kcal mol-')6 or ferrocene (ET35 kcal m~l-'),~' sensitisation experiments suggested that the cyclisation proceeds from the n-n* triplet excited state of the thiocarbonyl group.In conclusion, photolysis of acyclic and semicyclic mono- thioimides possessing a benzylic hydrogen atom at the 6-position gave y-lactams via a 1,5-diradical intermediate. Even a methoxy group attached to the 6-CH2 group is not sufficient to direct the hydrogen abstraction to that position, but indeed a phenyl is needed. This is in contrast to the simple ketones studied by Wagner.7 In some cases, viz. irradiation of semicyclic monothioimides, disproportionation took place and unsatur- ated thiols were obtained.Furthermore, the disproportionation involving 174-hydrogen shift appeared in five-membered semicyclic monothioimide, whereas six-membered semicyclic monothioimides gave the thermodynamically unstable olefin via 1,6-hydrogen shift. These photoreactions not only provide a useful synthesis of some 6-lactams, including pyrrolidine alkaloid analogues, but also yield important insight into hydrogen abstraction of thiocarbonyl compounds, since disproportionation to give unsaturated thiols is rare in ketone photochemistry. Experimental M.p.s were measured on a Yanagimoto micro melting point apparatus and are uncorrected. IR spectra were measured on a Shimadzu IR-420 spectrophotometer. 'H and 13C NMR spectra were recorded on Hitachi R-600 and JEOL GX-270 spectrometers with tetramethylsilane as internal standard, and J.CHEM. SOC. PERKIN TRANS. 1 1991 CDCl, as solvent unless otherwise stated. UV spectra were measured on a Shimadzu UV-200A UV-VIS-NIR recording spectrophotometer. Eikohsya 1 k W and 500 W high-pressure mercury lamps were used as the irradiation source. Silica gel (Merk, Kieselgel 60; 23MOO mesh) was used for flash column chromatography. Prepurution of Monothioimides.-All monothioimides were prepared by condensation of thioamides with the corresponding acid chlorides. The preparation of N-isovalerylthiobenzanilide la is given as an example. Triethylamine (300 mg, 3.0 mmol) was added dropwise to a solution of thiobenzanilide (600 nig, 2.8 mmol) and isovaleryl chloride (340 mg, 3.0 mmol) in dry benzene (30 cm3) at room temperature under nitrogen and the reaction mixture was then stirred for 2 h.The precipitated triethylamine hydrochloride was removed by filtration through a Celite column, the filtrate was evaporated, and the residual mixture was subjected to flash column chromatography (eluent: benzene-hexane, 4 : 1). N-Isovalerylthiobenzanilide la (770 mg, 92) was isolated as a red liquid and purified by molecular distillation. All other monothioimides 1b11were synthesized in the same manner. Crystalline monothioimides were re-crystallised from chloroform-hexane. N-Isovulerylthiobenzunilide la. B.p. 8amp;85 "C/lO-, mmHg; h,,,(c-C,H ,,)/nm 313 (E 8600) and 500 (160); v,,,(CHCl,)/cm-' 1700; 6, 0.86 (6 H, d, J 6.6 Hz, 2 x Me), 1.8-2.4 3 H, m, C(=O)CH, and CHMe, and 7.1-8.8 (10 H, m, ArH) (Found: C, 72.4; H, 6.4; N, 4.7.Cl8H1,NOS requires C, 72.69; H, 6.43; N, 4.70). N-(3-Methoxypropionyl)thiobenzunilide 1b. M.p. 60-61 "C; h,,,(c-C,H ,,)/nm 3 13 (1 2000) and 499 (1 80); v,,,(CHCl,)/cm-' 1700;6, 2.65 2 H, t, J6.6 Hz, C(=O)CH2, 3.32 (3 H, S, OMe), 3.65 (2 H, t, J 6.6 Hz, CH20) and 7.2-7.9 (10 H, m, ArH) (Found: C, 67.95; H, 5.7; N, 4.7. C17Hi7N02S requires C, 68.20; H, 5.72; N, 4.67). N-(3-Pheny1propionyl)thiobenzanilide lc. M.p. 67- 68 "C; h,,,(c-C,H ,/nm 313 (1 1 900) and 500 (190); v,,,(CHCl,)/cm-' 1700;6,2.77 2H, t, J7.0Hz,C(=O)CH2,2.89(2H,t, J7.0Hz, CH,Ph) and 7.s7.7 (15 H, m, ArH) (Found: C, 76.2; H, 5.6; N, 4.0.C2,H ,,NOS requires C, 76.49; H, 5.54; N, 4.05). N-(3-Pheny1butyryl)thiobenzanilide Id. M.p. 6@62 "C;h,,,(c-C6H,,)/nm 3 15 (10 500) and 502 (1 50); v,,,(CHCl,)/cm-' 1700; 6, 1.21 (3 H, d, J7.0 Hz, Me), 2.64 2 H, t, J4.2 Hz, C(=O)CH2, 2.9-3.6 (1 H, m, CHPh) and 6.7-7.6 (15 H, m, ArH) (Found: C, 76.6; H, 5.8; N, 3.9. C,,H,,NOS requires C, 76.84; H, 5.88; N, 3.89). p-Metho.q.- N -(3 -p hen y lpropion yl) th iobenzun ilide 1e. M .p. 65-67 "C; h,,,(c-C,H ,)/nm 343 (17 500) and 502 (260); v,,,(CHCl,)/cm-' 1700; 6, 2.75 2 H, t, J 6.6 Hz, C(=O)CH2, 2.87 (2 H, t, J6.6 Hz, CH,Ar), 3.73 (3 H, s, OMe) and 7.C7.7 (14 H, m, ArH) (Found: C, 73.5; H, 5.5; N, 3.7. C2,HZ1N02S requires C, 73.57; H, 5.63; N, 3.73).p-Methyl-N-(3-phenylpropionyl)thiobenzanilideIf. M.p. 67- 69 "C; h,,,(c-C,H,,)/nm 322 (13 700) and 502 (200); v,,,(CHCl,)/cm-' 1705; 6H2.29 (3 H, S, Me), 2.79 2 H, t, J 7.0 Hz, C(=O)CH2, 2.87 (2 H, t, J 7.0 Hz, CH,Ar) and 6.9-7.7 (14 H, m, ArH) (Found: C, 76.7; H, 5.8; N, 3.9. C23H21NOS requires C, 76.84; H, 5.88; N, 3.89). p-Chloro-N-(3-phenylpropionyl)thiobenzunilidelg. M.p. 1 12- 114deg;C; h,,,(c-C,H,,)/nm 319 (10 100) and 503 (230); v,,,(CHCl,)jcm-' 1710; 6H2.78 2 H, t, J 7.0 Hz, C(=O)CH2, 2.86 (2 H, t, J 7.0 Hz, CH,Ar) and 7.0-7.7 (14 H, m, ArH) (Found: C, 69.5; H, 4.85; N, 3.7. C2,Hl,CINOS requires C, 69.55; H, 4.77; N, 3.68). N-Isoi~ulerylpyrrolidine-2-thione1h. B.p. 70-72 "C/5 nimHg; h,,,(c-C,H I ,)/nrn 287 (12 500) and 426 (30); v,,,(CHCl,)/cm-' 1690: 6, 0.99 (6 H, d, J 6.6 Hz, 2 x Me), 1.8-2.4 (3 H, m, CHMe, + CH,), 3.19 2 H, t, J7.2 Hz, C(=S)CH,, 3.20 2 H, d, J 6.6 Hz, C(=O)CH, and 4.15 (2 H, t, J 7.2 Hz, NCH,) (Found: C, 58.1; H, 8.1; N, 7.6.C,H,,NOS requires C, 58.34; H, 8.15; N, 7.55). N-(3-Methoxypropionyl)pyrrolidine-2-thione li. B.p. 64-66 "C/2 mmHg; h,,,(c-C,H ,)/nm 287 ( 10 500) and 423 (20); v,,,(CHCl,)/cm-' 1690;6, 1.7-2.3 (2 H, m, CH,), 3.10 2 H, t, J 7.2 Hz, C(=S)CH2, 3.27 (3 H, s, OMe), 3.46 2 H, t, J 7.8 Hz, C(=O)CH2, 3.64 (2 H, t, J 7.8 Hz, OCH,) and 4.06 (2 H, t, J7.2 Hz, NCH,) (Found: C, 51.15; H, 7.0; N, 7.4. C,H,,NO,S requires C, 51.31; H, 6.99; N, 7.47). N-(3-Phenylpropionyl)pyrrolidine-2-thionelj. B.p. 59-60 "C/5 mmHg; h,,,(c-C6H12)/nm 287 (13 500) and 426 (30); v,,,(CHCl,)/cm-' 1700;8, 1.7-2.3 (2 H, m, CH,), 3.00 (2 H, t, J 6.6 Hz, CH,Ph), 3.14 2 H, t, J7.2 Hz, C(=S)CH,, 3.60 2, H, t, J 6.6 Hz, C(=O)CH,, 4.09 (2 H, t, J 7.2 Hz, NCH,) and 7.21 (5 H, s, ArH) (Found: C, 66.7; H, 6.5; N, 5.9.C13H1 ,NOS requires C, 66.92; H, 6.47; N, 6.00). N-(3-Phenylbutyryl)pyrrolidine-2-thione 1k. B.p. 104-106 "C/5 mmHg; h,,,(c-C6H12)/nm 289 (1 1 900) and 426 (20); v,,,(CHCl,)/cm-' 1700; 6,1.32 (3 H, d, J6.6 HL, Me), 1.6-2.2 (2 H, m, CH,), 3.12 2 H, t, J7.2 Hz, C(=S)CH,, 3.3-3.8 (1 H, m, CHMePh), 3.72 2 H, d, J3.0 Hz, C(=O)CH2, 4.01 (2 H, t, J7.2 Hz, NCH,) and 7.26 (5 H, s, ArH) (Found: C, 67.8; H, 6.9; N, 5.6. CI4H1,NOS requires C, 67.98; H, 6.92; N, 5.66".).N-(3-Phenylbutyryl)piperidine-2-thione11. B.p. 105-1 10 "Cjl mmHg; h,,,(c-C,H ,)/nm 305 (10 000) and 420 (40); v,,,(CHCl,)/cm-' 1700; 6,1.30 (3 H, d, J6.0 Hz, Me), 1.5-1.8 (4 H, m, 2 x CH,), 2.5-3.7 (7 H, m, CHMe + 3 x CH,) and 7.25 (5 H, s, ArH) (Found: C, 68.7; H, 7.25; N, 5.35. C15HI9 NOS requires C, 68.92; H, 7.32; N, 5.35). General Procedure .for the Photochemicd Reuction of' Monothioimides la-11.-A benzene solution of the mono-thioimide was irradaiated with a 1 kW high-pressure mercury lamp under argon at room temperature until the starting material had disappeared (TLC). After evaporation of the solvent, the residual mixture was subjected to flash chroma- tography with benzene-thy1 acetate (10: 1) as eluent. The crystalline photoproducts 2j and 2k were recrystallised from chloroform-hexane, whereas products 2c-2g, 21, 4k and 51 were liquid and decomposed on attempted distillation.5-Mercupto-1,4,5-triphenylpyrrolidin-2-one2c. This photo- product was obtained as a mixture of two stereoisomers in the ratio 8 :3. v,,,(CHCl,)/cm-' 1700; m/z (CI) 346 (M + 1). (Major isomer): 6, 1.60 (1 H, s, SH), 2.96 (1 H, dd, J 16.6 and 7.5 Hz, 3-H), 3.27 (1 H, dd, J 16.6 and 9.6 Hz, 3-H),4.04 (1 H, dd, J9.6 and 7.5 Hz, 4-H) and 6.8-7.7 (15 H, m, ArH): 6, 35.4 (t, C-3), 55.3 (d, C-4), 82.7 (s, C-5), 126.5 (d, Ph), 126.6 (d, Ph), 128.0 (d, Ph), 128.3 (d, Ph), 128.4 (d, Ph), 128.5 (d, Ph), 128.6 (d, Ph), 128.9 (d, Ph), 129.0 (d, Ph), 136.1 (s, Ph), 136.5 (s, Ph), 142.1 (s, Ph) and 174.0 (s).(Minor isomer): 6, 2.46 (1 H, s, SH), 2.83 (1 H, dd, J 16.8 and 8.2 Hz, 3-H), 3.04 (1 H, dd, J 16.8 and 7.3 Hz, 3-H), 4.05 (1 H, dd, J 8.2 and 7.3 Hz, 4-H) and 6.8-7.7 (15 H, m, ArH): 6, 35.2 (t, C-3), 55.7 (d, C-4), 81.3 (s, C-5), 134.8 (s, Ph), 136.5 (s, Ph), 139.1 (s, Ph) and 172.8 (s). 5-Mercupto-4-methyl-1,4,5-triphenylpyrrolidin-2-one2d. This photoproduct was obtained as a mixture of two stereoisomers in the ratio 3:2. v,,,(CHCl,)/cm-' 1700; mi: (CI) 360 (M + 1). (Major isomer): 6, 1.58 (1 H, s, SH), 1.87 (3 H, s, Me), 2.49 (1 H, d, J 16.0 Hz, 3-H), 3.40 (1 H, d, J 16.0 Hz, 3-H) and 7.0-7.5 (15 H, m, ArH); 6, 26.2 (9, Me), 41.7 (t, C-3), 52.0 (s, C-4), 85.6 (s, C-5), 139.7 (s, Ph), 140.5 (s, Ph), 141.0 (s, Ph) and 174.3 (s, C=O).(Minor isomer): 6, 1.23 (3 H, s, Me), 2.14 (1 H, s, SH), 2.80 (1 H, d, J 15.9 Hz, 3-H), 3.28 (1 H, d, J 15.9 Hz, 3-H) and 7.0-7.5 (15 H, m, ArH); 6, 25.1 (9, Me), 44.6 (t, C-3), 50.8 (s, C-4), 85.2 350 (s, C-5), 136.9 (s, Ph), 137.0 (s, Ph), 143.2 (s, Ph) and 173.3 (s, C=O). 5-Mercapto-5-( p-methoxyphenyr)- 1,4-diphenylpyrrolidin-2-one 2e. This photoproduct was obtained as a mixture of two stereoisomers in the ratio 3: 1. v,,,(CHCl,)/cm-' 1700; m/z (CI) 376(M + 1). J. CHEM. SOC. PERKIN TRANS. 1 1991 7.5 (5 H, m, ArH); 6,25.9 (t, C-7), 36.9 (t, C-3), 40.4 (t, C-8), 40.8 (4 C-6), 53.7 (d, C-4), 82.1 (s, C-5), 127.5 (d, Ph), 127.7 (d, Ph), 128.9 (d, Ph), 139.7 (s, Ph) and 172.3 (s, C=O); m/z (SIMS) 234 (M + 1) (Found: C, 66.8; H, 6.45; N, 6.0).5-Mercapto-4-methyl-4-phenyl-1 -azabicyclo 3.3.01octan-2- one 2k.M.p. 105-107 "C; v,,,(CHCl,)/cm-' 6, 1680; 1.39 (3 H, (Major isomer): 8, 1.99 (1 H, s, SH), 2.94 (1 H, dd, J 16.6 and 7.5 Hz, 3-H), 3.29 (1 H, dd, J 16.6 and 10.2 Hz, 3-H), 3.82 (3 H, s, MeO), 4.05 (1 H, dd, J 10.2 and 7.5 Hz, 4-H) and 6.6-7.7 (14 H, m, ArH); 6, 35.3 (t, C-3), 55.3 (q, MeO), 67.5 (d, C-4), 82.5 (s, C-5), 113.6 (d, Ph), 126.6 (d, Ph), 126.7 (d, Ph), 128.3 (d, Ph), 128.5 (d, Ph), 128.8 (d, Ph), 128.9 (d, Ph), 129.4 (d, Ph), 133.8 (s, Ph), 136.1 (s, Ph), 136.5 (s, Ph), 159.5 (s, Ph) and 174.0 (s, C=O). (Minor isomer): 6, 2.42 (1 H, s, SH), 2.82 (1 H, dd, J 16.8 and 8.1 Hz, 3-H), 2.98 (1 H, dd, J 16.8 and 4.3 Hz, 3-H), 3.78 (3 H, s, MeO), 4.05 (1 H, dd, J8.1 and 4.3 Hz, 4-H) and 6.67.7 (14 H, m, ArH); 6, 40.1 (t, C-3), 55.1 (4, MeO), 69.1 (d, C-4), 82.2 (s, C-5), 134.3 (s, Ph), 135.2 (s, Ph), 137.4 (s, Ph), 158.9 (s, Ph) and 170.0 (s, C=O).5-Mercapto-1,4-diphenyl-5-(p-tolyl)pyrrolidin-2-one2f. This photoproduct was obtained as a mixture of two stereoisomers in the ratio 3: 1. v,,,(CHC13)/cm-' 1695; m/z (CI) 360 (M + 1). (Major isomer): 6H 1.60 (1 H, s, SH), 2.35 (3 H, s, Me), 2.95 (1 H, dd, J 16.5 and 7.3 Hz, 3-H), 3.26 (1 H, dd, J 16.5 and 9.5 Hz, 3-H), 4.03 (1 H, dd, J9.5 and 7.3 Hz, 4-H) and 6.9-7.6 (14 H, m, ArH); 6, 21.0 (q, Me), 35.4 (t, C-3), 55.3 (d, C-4), 82.7 (s, C-5), 126.6 (d, Ph), 127.8 (d, Ph), 128.2 (d, Ph), 128.3 (d, Ph), 128.5 (d, Ph), 128.6 (d, Ph), 128.9 (d, Ph), 129.1 (d, Ph), 136.3 (s, Ph), 136.5 (s, Ph), 138.2 (s, Ph), 139.1 (s, Ph) and 174.1 (s, C=O).(Minor isomer): 6, 2.20 (1 H, s, SH), 2.30 (3 H, s, Me), 2.81 (1 H, dd, J 16.8 and 7.9 Hz, 3-H), 2.99 (1 H, dd, J 16.8 and 12.6 Hz, 3-C), 4.00 (1 H, dd, J 12.6 and 7.9 Hz, 4-C) and 6.9- 7.6 (14 H, m, ArH); 6, 20.9 (9, Me), 35.3 (t, C-3), 55.7 (d, C-4), 81.4 (s, C-5), 132.5 (s, Ph), 134.7 (s, Ph), 136.2 (s, Ph), 136.7 (s, Ph) and 173.0 (s, C=O). 5-(p-Chlorophenyl)-5-rnercapto-1,4-diphenylpyrrolidin-2-one 2g. This photoproduct was obtained as a mixture of two stereoisomers in the ratio 3: 1. v,,,(CHCl,)/cm-' 1695; m/z (CI) 380(M + 1). (Major isomer): 6, 1.57 (1 H, s, SH), 2.94 (1 H, dd, J 16.5 and 7.4 Hz, 3-H), 3.31 (1 H, dd, J 16.5 and 10.3 Hz, 3-H), 3.99 (1 H, dd, J 10.3 and 7.4 Hz, 4-H) and 6.8-7.6 (14 H, m, ArH); 6, 35.3 (t, C-3), 55.5 (d, C-4), 82.2 (s, C-5), 126.5 (d, Ph), 126.6 (d, Ph), 128.0 (d, Ph), 128.2 (d, Ph), 128.4 (d, Ph), 128.5 (d, Ph), 128.6 (d, Ph), 128.9 (d, Ph), 134.5 (s, Ph), 135.5 (s, Ph), 136.3 (s, Ph), 140.7 (s, Ph) and 174.0 (s, C=O).(Minor isomer): 6H 2.07 (1 H, s, SH), 2.86 (1 H, dd, J 16.8 and 8.2 Hz, 3-H), 3.01 (1 H, dd, J 16.8 and 6.4 Hz, 3-H), 4.02 (1 H, dd, J8.2 and 6.4 Hz, 4-H) and 6.8-7.6 (14 H, m, ArH); 6, 35.0 (t, C-3), 55.6 (d, C-4), 80.8 (s, C-5), 134.4 (s, Ph), 136.6 (s, Ph), 138.0 (s, Ph), 142.0 (s, Ph) and 172.6 is, C=O). 5-Mercapto-4-phenyl-1-azabicyclo3.3.0octan-2-one 2j. (Major isomer): m.p.10amp;101 "C; v,,,(CHCl,)/cm-' 1690; 6, 1.52 (1 H, s, SH), 2.2-2.3 (1 H, m, 6-H), 2.3-2.4 (2 H, m, 6- and 7-H), 2.5-2.7 (1 H, m, 7-H), 2.69 (1 H, dd, J 15.5 and 6.9 Hz, 3-H), 3.3-3.4 (1 H, m, 8-H), 3.38 (1 H, dd, J 15.5 and 12.8 Hz, 3-H), 3.55-3.75 (1 H, m, 8-H), 3.74 (1 H, dd, J 12.8 and 6.9 Hz, 4-H) and 7.25-7.45 (5 H, m, ArH); 26.3 (t, C-7), 38.4 (t, C-3), 40.4 (t, C-8), 43.1 (t, C-6), 54.4 (d, C-4), 82.0 (s, C-5), 127.8 (d, Ph), 128.1 (d, Ph), 128.6 (d, Ph), 137.0 (s, Ph) and 171.1 (s, C=O); m/z (SIMS) 234 (M + 1) (Found: C, 66.7; H, 6.5; N, 5.9. C13H15NOS requires C, 66.92; H, 6.47; N, 6.00). (Minor isomer): m.p. 71-73 OC; v,,,(CHCl,)/cm-' 1690; 6, 1.3-1.5 (1 H, m, 6-H), 1.5-1.7 (1 H, m, 6-H), 1.8-2.0 (1 H, m, 7-H), 2.2-2.4 (1 H, m, 7-H), 2.55 (1 H, s, SH), 2.71 (1 H, d, J 17.1 Hz, 3-H), 3.2-3.3 (1 H, m, 8-H), 3.4-3.5 (1 H,m, 8-H), 3.50(1 H, dd, J 17.1 and 6.7 Hz, 3-H), 3.90 (1 H, d, J6.7 Hz, 4-H) and 7.2-- s, Me), 1.62 (1 H, s, SH), 2.1-2.3 (1 H, m, 6-H), 2.3-2.4 (1 H, m, 6-H), 2.50(1 H, d, J 15.2 Hz, 3-H), 2.5-2.7 (2 H, m, 7-H,), 3.2-3.4 (1 H3m,8-H),3.4-3.6(1H,m,8-H),3.67(1H,d,J15.2Hz,3-H) and 7.2-7.5 (5 H, m, ArH); 6, 23.3 (t, C-7), 27.0 (q, Me), 36.5 (t, C-3), 40.2 (t, C-S), 46.6 (t, C-6), 52.9 (d, C-4), 85.0 (s, C-5), 126.4 (d, Ph), 127.1 (d, Ph), 128.7 (d, Ph), 144.2 (s, Ph) and 170.8 (s, c=o); m/z (CI) 248 (M + 1) (Found: C, 68.0; H, 6.9; N, 5.7.C14H,,NOS requires C, 67.97; H, 6.94; N, 5.66). N-( 3'- Phenylbut-3'-enoyl)pyrrolidine-2-thiol4k.v,,,(CHCl,)/ cm-' 1685 and 1635; 6, 1.26 (1 H, s, SH), 1.6-2.2 (6 H, m, 3-, 4- and 2'-H2), 2.8-3.2 (1 H, m, 5-H), 3.4-3.8 (2 H, m, 2- and 5-H), 5.19 (1 H, d, J0.6 Hz, C=CH), 5.52 (1 H, d, J0.6 Hz, CKH) and 7.2-7.6 (5 H, m, ArH); 6, 24.3 (t, C-4), 33.0 (t, C-H or -3), 42.0 (t, C-5), 46.6 (t, C-2'), 56.2 (d, C-2), 114.9 (t, C-4'), 125.7 (d, Ph), 127.8 (d, Ph), 128.4 (d, Ph), 140.2 (s, C-3' or Ph), 141.2 (s, Ph or C-3') and 168.9 (s, C=O); m/z (CI) 248 (M + 1).6-Mercapto-7-methyl-7-phenyl-1-azabicyclo4.3.0nonan-9-one 21. (Major isomer): obtained in 16 yield, v,,,(CHCl,)/cm-' 1680;6, 1.2-1.5 (2 H, m, 3- or4-H2), 1.49 (3 H, S, Me), 1.57 (1 H, s, SH), 1.7-2.1 (2 H, m, 4- or 3-H,), 2.1-2.25 (2 H, m, 5-H2), 2.34 (1 H,d,J15.9Hz,8-H),2.7-2.9(1H,m,2-H),3.34(1H,d,J15.9 Hz, 8-H), 4.0-4.1 (1 H, m, 2-H) and 7.2-7.4 (5 H, m, Ph); 6,20.2 (q, Me), 23.5 (t, C-3 or -4), 26.2 (t, C-4 or -3), 34.5 (t, C-5),37.7 (t, C-8), 42.2 (t, C-2), 51.1 (s, C-7), 78.5 (s, C-6), 126.8 (d, Ph), 127.3 (d, Ph), 128.3 (d, Ph), 143.3 (s, Ph) and 172.6 (s, C=O); m/z (CI) 261 (M + 1).(Minor isomer): 11 yield, v,,,(CHCl,)/cm-' 1670;6, 0.9-1.2 (2 H, m, 3- or 4-H2), 1.4-1.7 (2 H, m, 4- or 3-Hz), 1.63 (3 H, s, Me), 1.7-2.0 (2 H, m, 5-H,), 1.99 (1 H, s, SH), 2.64 (1 H, d, J 16.8 Hz, 8-H), 2.96 (1 H, J 16.5 Hz, 8-H), 3.63.7 (1 H, m, 2-H), 3.94.1 (1 H, m, 2-H) and 7.2-7.4 (5 H, m, ArH); 6,20.6 (q, Me), 23.7 (t, C-3 or -4), 26.5 (t, C-4 or -3), 35.3 (t, C-5), 37.6 (t, C-8), 44.0 (t, C-2), 48.0 (s, C-7), 78.0 (s, C-6), 125.8 (d, Ph), 127.0 (d, Ph), 128.4 (d, Ph), 143.3 (s, Ph) and 173.0 (s, C=O); m/z (CI) 261 (M + 1).N-(p-Met hylc innamo y l)piper idine-2-thiol51. (Z)-isomer :ob-tained in 26 yield, v,,,(CHCl,)/cm-' 1640; 6, 1.2-2.1 (7 H, m, 3 x CH2 + SH), 2.25 (3 H, s, Me), 2.3-2.4 (1 H, m), 3.4-3.9 (2 H, m), 6.21 (1 H, br s, C=CH), 7.1-7.5 (5 H, m, ArH); 6, 17.9 (q, Me), 19.3 (t, C-3 or -4), 25.7 (t, C-4 or -3), 32.1 (t, C-5), 41.2 (t, C- 2), 50.4 (d, C-6), 119.6 (d, C-CX),125.9 (d, Ph), 128.4 (d, Ph) 128.5 (d, Ph), 139.3 (s, Ph or C-p), 141.6 (s, C-p or Ph) and 167.8 (s, C=O); m/z (CI) 261 (M + 1). ( E)-isomer: 1 1 yield, v,,,(CHCl,)/cm-' 1640; 6H 1.1-2.1 (6 H, m, 3 x CH,), 2.18 (3 H, d, J 1.5 Hz, Me), 2.62 (1 H, s, SH), 3.0-3.2 (1 H, m), 3.5-3.7 (1 H, m), 4.24.4 (1 H, m), 5.88 (1 H, q, J 1.5 Hz, C=CH) and 7.2-7.6 (5 H, m, ArH); 6, 19.0 (t, C-3 or 4-H), 24.3 (q, Me), 25.0 (t, C-4 or -3), 31.6 (t, C-5), 41.2 (t, C-2), 50.1 (d, C-6), 120.6 (d, C-x), 127.4 (d, Ph), 128.1 (d, Ph), 128.3 (d, Ph), 139.9 (s, Ph or C-p), 143.3 (s, C-p or Ph) and 167.9 (s, C=O); m/z (CI) 261 (M + 1).Sensitisation and Quenching of' N-(3- Phen~~lpropion?,~p~~r- rolidine-2-thione 1j.-Five Pyrex tubes were irradiated at 365 nm with a 500 W high-pressure mercury lamp in a merry-go- round apparatus. The tubes contained starting material lj (0.02 mol drn-,), lj and Michler's ketone, lj and thioxanthone, lj and stilbene, and lj and ferrocene, respectively. After removal of benzene the extent of reaction was determined by 'H NMR spectroscopy.The 365 nm radiation was isolated by using a uranil glass filter. Concentration of each sensitiser was adjusted so that 57; or less of the incident light was absorbed J. CHEM. SOC. PERKIN TRANS. 1 1991 by the imide lj (in sensitisation) or by the sensitiser (in quench- ing). References 1 V. Ramamurthy, Organic Photochemistry, Mercel Dekker, New York and Basel, 1985, vol. 7, pp. 231-329; J. D. Coyle, Tetrahedron, 1985, 41, 5393. 2 P. de Mayo and R. Suau, J. Am. Chem. SOC., 1974,, 6807; K. W. Ho and P. de Mayo, J. Am. Chem. SOC.,1979, 101, 5725; S. Basu, A. Couture, K. W. Ho, M. Hoshino, P. de Mayo and R. Suau, Can. J.Chem., 1981,59,246; A. Couture, J. Gomez and P. de Mayo, J. Org. Chem., 1981,46,2010. 3 (a) C. Fombert, J. L. Fourrey, P. Jouin and J. Moron, Tetrahedron Lett., 1974, 3007; (b) C. Marazano, J. L. Fourrey and B. C. Das, J. Chem. SOC., Chem. Commun., 1977, 742; (c) P. de Mayo, L. K. Sydnes and G. Wenska, J. Org. Chem., 1980, 45, 1549; M. Sakamoto, H. Aoyama and Y. Omote, (d) J. Org. Chem., 1984, 49, 396; (e) Tetrahedron Lett., 1986, 27, 1335; (f)M. Machida, K. Oda 351 and Y. Kanaoka, Chem. Pharm. Bull., 1985,33,3352; (g)J. D. Coyle, P. A. Rapley, J. Kamphuis and H. J. T. Bos, J. Chem. SOC., Perkin Trans. I, 1985, 1957; (h)K. Oda, M. Machida, K. Aoe, Y. Nishibata, Y. Sat0 and Y. Kanaoka, Chem. Pharm. Bull., 1986,34,1411,4414; (i) T. Nishio and Y. Omote, Synthesis, 1986, 54; (J) K. Oda, M. Machida and Y. Kanaoka, Heterocycles, 1988, 27, 2417; (k) M. Sakamoto, S. Watanabe, T. Fujita and T. Yanase, J. Org. Chem., 1990,55,2986. 4 M. Sakamoto,H. Aoyama and Y. Omote, J. Org.Chem., 1984,49,1837. 5 M. Sakamoto, S. Watanabe, T. Fujita, M. Tohnishi, H. Aoyama and Y. Omote, J. Chem. SOC., Perkin Trans. I, 1988,2203. 6 S. L. Murov, Handbook of Photochemistry, Marcel Dekker, New York, 1973. 7 P. J. Wagner, P. A. Kelso, A. E. Kemppainen and R. G. Zepp, J. Am. Chem. SOC., 1972,94,7500. Paper 0/03096D Received 9th July 1990 Accepted 29th August 1990