摘要:
1934 J.C.S. Perkin ISynthesis of a-M ethylene- y-lactones involving Baeyer-ViI I iger Oxidationof a-Su bstituted CyclobutanonesBy S. Mubarik Ali and Stanley M. Roberts, The Ramage Laboratories, Department of Chemistry and AppliedThe previously reported 7-exo-halogeno-7-endo-methylbicyclo[3.2.0] heptan-6-ones (3) and (1 3) and 7-exo-bromo-7-endo-methylbicyclo[3.2.0] hept-2-en-6-one (1 ) were converted into the corresponding a-methylene-y-lactones (31 ) and (33) in two steps, involving Baeyer-Villiger oxidation and dehydrohalogenation. Similarly,7-exo-bromo-7-endo-isopropylbicyclo[3.2.0] hept-2-en-6-one (1 1 ) gave the isopropylidene-lactone (34). andthe bromomethylbicyclo-octanone (5) gave the lactone (32). In contrast, oxidation and dehydrobromination of7 -en do - b ro m o - 7 - exo - met h y I bi c y cl o [ 3.2 .O] he p t - 2 - en - 6 - o n e ( 2 ) a n d 7 - en do - b ro m o - 7 - exo - met h y I b i c y c I o [ 3.2 .O] -heptan-6-one (4) gave the ccp-unsaturated lactones (36) and (35), respectively.Chemistry, University of Salford, Salford M5 4WTTHE biological activity of compounds possessing thea-methylene-y-lactone unit has led to recent interest inthe development of synthetic routes to this system.2In particular, pathways to compounds in which thea-methylene-y-lactone system is cis- (A) or trans-fused(B) to an alicyclic ring have been sought.A route to cis-fused bicyclic a-methylene-y-lactones[type (A)] that had been overlooked hitherto involvesthe three-step elaboration of an alkene as illustrated inOlefinresultant cyclobutanone (step ii) and modification of Rand R' to give the exocyclic methylene group (step iii).The role of the substituents R and R' is twofold: firstthey must be readily convertible into the exocyclic-methylene function and, secondly, they must direct themode of ring expansion in the preceding oxidation step.With these two factors in mind we chose to investigatethe feasibility of the sequence using R' = halogen andR = alkyl; advantageously, the properties of theappropriate ketens had been described previ~usly.~Various cyclic alkenes were used as substrates for thealkylhalogenoketens in the initial cycloaddition reaction ;the results are summarized in the Table.By employinghexane as the solvent and by conducting the cyclo-additions at or above room temperature endo-alkyl-exo-halogenocyclobutanone derivatives were formed asSCHEME 1Cycloaddition of alkylhalogenoketens t o cyclicReactionKeten temp.("C) Yield (%)Bromo(methy1) ketenCy clopentadieneCyclopenteneCvclohexene256565704050D\hydropyran J 25 70Cyclopentadiene Chloro( methyl) keten 40 86Cyclopentadiene Bromo (isopropyl) keten 40 74olefinsProducts Reference [yield (%) ;(isomer ratio) isomer ratio](11, (2) (1.4: 1) 5 [--; 1.1 : 11(31, (4) ( 8 : 1) 6 [37; 1.3: 11(51, (6) (1.1 : 1)(7), (8) (1.5: 1) a c50; 0.6 : 11(9), (10) (4.5: 1) 6 [61; 4.5: 11( 1 1 ) , (12) (7 : 1) 5 [78; 7.4: 13a W. T. Brady and R. Roe, J . Amer. Chem. SOC., 1971, 93, 1662.Scheme l.3 The route entails cycloaddition of a ketenand olefin (step i) , Baeyer-Villiger oxidation of theA.T. McPhail, K. D. Onan, K.-H. Lee, T. Ibuka, and H.-C.Huang, Tetrahedron Letters, 1974, 3203; K.-H. Lee, T. Ibuka,M. Kozuka, A. T. McPliail and K. D. Onan, ibid., 1975, 2287;K.-H. Lee, T. Ibuka, S.-H. Kim, B. R. Vestal, and I. H. Hall,J. Medicin. Chem., 1975, 18, 812 and references therein.R. B. Gammill, C. A.Wilson, and T. A. Bryson, Synth. Comm., 1975,4, 245; T. Minami,I. Niki, and T. Agawa, J . Org. Chem., 1974,39,3236; L. S. Hegedus,S. D. Wagner, E. L. Waterman, and K. Siirala-Hansen, ibid.,1975, 40, 593; J. A. Marshall and W. R. Snyder, ibid., p. 1656;Synth. Comm., 1975, 5, 43; P. A. Grieco, N. Marinovic, andM. Miyashita, J . Org.Chem., 1975, 40, 1670; M. Kato, M.Kageyama, R. Tanaka, K. Kuwahara, and A. Yoshikoshi,ibid., p. 1932; D. Caine and G. Hasenhuettl, Tetrahedron Letters,1975, 743; P. A. Grieco, C . J. Wang, and S. D. Burke, J.C.S.Chem. Comm., 1975, 537; A. D. Harmon and C. R. Hutchinson,J . Org. Chem., 1975, 40, 3474.P. A. Grieco, Synthesis, 1975, 67;major p r o d ~ c t s . ~ ~ ~ Separations of the isomeric productswere achieved readily by distillation and/or columnchromatography.As expected, the oxidations of the bicycloalkanones(3)-(5), (7), and (13) with m-chloroperbenzoic acidproceeded with migration of the bridgehead carbon atomexclusively to give the corresponding lactones (14)-(18) in high yield.7 Baeyer-Villiger oxidations of thePreliminary communication, S.M. Ali and S. M. Roberts,J.C.S. Chem. Comna., 1975, 887.W. T. Brady, Synthesis, 1971, 415.5 W. T. Brady and R. Roe, J - Amer. Chem. SOC., 1970, 92,6 W. T. Brady, R. Roe, E. F. Hoff, and F. H. Parry, J . Amer.7 J. B. Lee and B. C . Uff, Quart. Rev., 1967, 21, 429; P. A.4618.Chem. SOC., 1970, 92, 146.Grieco, J . Org. Chem., 1972, 37, 23631976 1935analogous bicycloalkenones (l), (2), and (9)-(11) wereconducted under milder conditions in order to minimizeconcurrent epoxidation. Buffered peracetic acid oxi-by reaction with HBr and subsequent rearrangement(Scheme 2).8 The lability of the bromohydrin (24) wasdemonstrated by treating the ketone (2) with N-bromo- Qy H @OR' H WRi H. . . . . . R' . . . .fi2 A A 2 ti R2(1) R'=Me, R2=Br (3) R'=Me, R2=Br ( 5 ) R'=Me, R2=8r, X=CH,(2) R1=Br, R2=Me (6) R'=Br, R2=Me, X =CH2(9) R'=Me.R%C! (13) R'=Me,R2=CL (7) R'=Me, R2=Br, X =O(10) R ' = c L , R ~ = M ~ (8) R'=Br, R2= Me, X =O(11) R'=Pri,R2=Br(121 R'=Br, R2=Pri( 4 ) R'=Br, R2=Medizecl the endo-halogenobicycloheptenones (2) and (10)to the corresponding lactones (19) and (20) exclu-sively.More vigorous oxidation of the ketone (2) gave. .. - ..H a2 H R2 i r(19) R'=Br, R2=Me (14) R'=Me, R2=Br (16) X=CH2(20) R'=CI, R2=Me (15) R'=BT. R Z M ~ (17) x=o(25) R'=Me, R*=Er(26) R'= Me, R2= CI(29) R'=Pr ', RGBr(18) R'=Me, R2=C1a mixture containing the lactone (19) and the epoxy-lactone (21) as major products. Omission of buffer in(21) (221 (27) R'=Me, R2=Br(28) R'=Me, R2=C1(30) R ' = P ? , R ~ = B ~the peracetic acid oxidation of compound (2) led to adecreased yield of the lactone (19) and production of theacetamide (NBA) in aqueous acetone; a good yield ofthe rearranged lactone (22) was obtained.The exo-halogenobicyclo[3.2.0]hepten-6-ones (1) and(9) underwent Baeyer-Villiger ring expansion moreslowly than the ercdo-halogeno-isomers, owing, no doubt,to the unfavourable influence of the halogen atom on theapproach of the peracetic acid to the carbonyl carbonatom from the exo-face in the rate-determining step ofthe o~idation.~ However, oxidation conditions wereestablished whereby the sole product isolated fromreactions of compounds (1) and (9) was the correspondinglactone (25) or (26).Prolonged oxidation gave rise toappreciable amounts of the corresponding endo-epoxy-lactone (27) or (28).Baeyer-Villiger oxidation of the bromo-ketone (1 1)proceeded very slowly and, after chromatography, thelactone (29) and the endo-epoxy-lactone (30) were isolatedin poor yield.The configuration of the three-membered ring in theoxirans (2l), (27), (28), and (30) is conveniently ascer-tained by n.m.r.spectroscopy: most noticeably, thatproton at C-8 which is adjacent to the oxiran oxygenatom, resonates at lower field. It is noteworthy that7-exo-halogenobic yclo [3.2 .O] heptenones give endo-epoxy-lactones,1° whereas 7-e.ndo-halogenobicyclo[3.2.0]hepten-ones yield exo-epoxylactones preferentially.The required elimination of HBr from the 7-exo-bromo-lactones (14), (16), (25), and (29) occurred readily ontricyclic lactone (22).We envisage that the latter treatment with 1,5-diazabicyclo[4.3.0]non-5-ene (DBN)compound is formed from the e&o-epoxyketone (23) in hot toluene to give the corresponding a-alkylidene-y-8 2. Grudzinski and s. M. Roberts, J.C.S. perkin 1, 1975, la&neS (31)-(34).11 Similarly, the 7-exo-chloro-lactone1767. lo E. J. Corey and R. Noyori, Tetrahedron Letters. 1970, 307.J. L. Mateos and H. Menchaca, J . Org. Chem., 1964, 29, l1 A. E. Green, J.-C. Muller, and G. Ourisson, Tetvahedron2026. Letters, 1972, 2489, 33751936 J.C.S. Perkin I(18) eliminated HC1 to give compound (31) on moreprolonged treatment with DBN. In contrast, the halo-geno-lactones (17) and (26) gave no identifiable productswhen treated with the base.Not unexpectedly, base-catalysed elimination of HBrfrom the 7-endo-bromolactone (15) gave the ap-un-saturated lactone (35) ,12 whereas the unsaturated analogue(19) gave the diene (36) as the sole product in almostquantitative yield.We believe that (36) is formed fromthe expected product (37) by a series of base-induced 1,3-and 1 $-hydrogen shifts (Scheme 3) ;12 molecular modelsMe' \Me(34)indicate that the observed product (36) is considerablyless strained than the postulated intermediate (37).In conclusion, the route described in Scheme 1 has beenshown to be useful for the synthesis of compounds inwhich an a-methylene-y-lactone unit is cis-fused to analicyclic ring system.However, there are two majorinadequacies. First, the requisite a-halogen atom (R'in Scheme 1) must be trams-oriented to a vicinal p-substituent to avoid formation of an endocyclic doublebond. Secondly, the synthetic sequence will be oflimited utility when the cycloaddition of keten and anprepared by reported method^.^, The isomeric productswere separated by distillation and/or column chromato-graphy (CHCl,) .Pwparation of the Bicyclic Lactones (14)-(20), (25), (26),ar,d (29) .--Method A. To the appropriate bicyclic ketone(0.01 mol) in chloroform (30 ml) were added m-chloroper-benzoic acid (0.015 mol) and sodium hydrogen carbonate(0.015 mol). The mixture was stirred a t room temperature.The excess of peroxy-acid was decomposed by washing withaqueous 10% sodium sulphite.Finally the chloroformlayer was washed with saturated sodium hydrogen carbon-ate solution, dried, and evaporated. The products were(35) (36)purified by column chromatography with chloroform aseluant.Method B. To the bicyclic ketone (0.01 mol) in aceticacid (10 ml) were added a solution of hydrogen peroxide(307; in water; 0.03 mol) in acetic acid (5 ml) and sodiumacetate (0.01 mol). When the reaction was complete thesolution was diluted with water (100 ml) and extracted withether (3 x 25 ml). The combined extracts were washedwith aqueous sodium sulphite solution (10% ; 2 x 15 nil)and water (3 x 15 ml), dried, and evaporated. The residuewas purified as in method A.(a) 4-exo-Brouno-4-endo-1.nethy2-2-oxabicycZ~[3.3.O]octun-3-unsymmetrical alkene is non-specific.Further studiesare being pursued in an effort to circumvent thesedifficulties.EXPERIMENTALDistill-ations were accomplished by using the Buchi Kugelrohr(bulb-to-bulb) system and the b.p.s reported are oventemperatures at distillation. N.m.r. spectra were obtainedwith a Varian EM-360 or Perkin Elmer R-32 spectrometer(CC1, or CDCI, as solvent). 1.r. spectra were recordedwith a Perkin-Elmer 257 spectrometer for neat films unlessotherwise stated. Silica gel MFC was used for columnchromatography. Anhydrous sodium sulphate was used as adrying agent for solutions in organic solvents.Prepavation of the Bicyclic Ketones (1)-( 13). These werel2 A. E. Green, J.-C. Muller, and G.Ourisson, J. Org. Chem.,M.p.s were taken by the capillary tube method.1974, 39, 186one (14) was obtained from the bicyclic ketone (3) (methodA; 24 h) as an oil (60%), b.p. 87-90' at 0.003 mmHg, v,,1 770, 1 450, 1 150, and 1 080 cm-l, 6 4.75 (1 H, m, H-l), 2.8(1 H, in, H-5), 1.6 (3 H, s, Me), and 1.5 (6 H, m) (Found:C, 44.0; H, 5.0. C,HllBrO, requires C, 43.8; H, 5.0%).(b) 4-endo-Bronzo-4-exo-Irtethyl-2-oxaba'cycZo[3.3.0Joctan-3-one (151, from the bicyclic ketone (4) (method A; 15 h), wasan oil (930/,), b.p. 90-92' at 0.05 mmHg, vmX. 1 780, 1 450,1210, and 1085 cm-l, 6 4.9 (1 H, m, H-l), 2.75 (1 H, m,H-5), 2.0 (3 H, s, Me), and 1.8 (6 H, m) (Found: Mi,217.9938. C8HllBr0, requires &f, 217.9942).(c) 9-exo-Bromo-9-endo-methyl-7-oxabicyclo[4.3.0]nonan-8-one (16) l2 was obtained from the bicyclic ketone (5)(method A; 20 h) as an oil (63%), v,,,.1770, 1450, and1 130 cm-l, 8 4.8 (1 H, m, H-6), 2.3 (1 H, m, H-l), 1.7 (3 H,s, Me), and 1.5 (8 H, m).(d) 9-exo-Bromo-9-endo-meth~~Z-2,'i-dioxabicycZo[4.3.0]-qzonan-8-one (17), from the bicyclic ketone (7) (method A1976 193716 h), was an oil (65y0), b.p. 95-97" a t 0.04 mmHg, vmX.1780, 1450, 1190, and 1090 cm-l, 6 4.7 (1 H, m, H-6),4.0 (1 H, d, J 2 Hz, H-l), 3.6 (2 H, m, 2 x H-3), 1.7 (4 H,ni), and 1.8 (3 H, s, Me) (Found: M+, 233.9894. C,H1,BrO,requires M , 233.9891).(e) 4-exo-ChZoro-4-endo-met~zyZ-2-oxab~cycZo~3.3.O]octan-3-092e (18), from the bicyclic ketone (13) (method A; 16 h), wasa liquid (91%), b.p. 85-86" a t 0.02 mmHg, v,,,.1780,1450, 1150, and 1090 cm-1, 6 5.0 (1 H, rn, H-l), 2.9 (1 H,111, H-5), 1.8 (6 H, m), and 1.65 (3 H, s, Me) (Found: C,55.2; H, 6.3. C,Hl1C1O2 requires C, 55.2; H, 6.3%).( f ) 4-endo-Brouno-4-exo-methyl-2-oxa~~cycZo[3.3.O]oct-6-en-%one (19), from the bicyclic ketone (2) (method A ; 5 'C;3 h), was an oil (75y0), b.p. 90-95" a t 0.005 mmHg,vnlap, 1770, 1440, 1180, and 1095 cm-l, 6 5.75 (2 H, m,H-6 and -7), 5.1 (1 H, m, H-l), 3.5 (1 H, m, H-5), 2.75(2 H, m, 2 x H-8), and 2.0 (3 H, s, Me) (Found: Mf,2 15.9786.Reaction under the same conditions but a t room tempera-ture gave the lactone (19) 25% and the exo-epoxy-Zactone(21) as fine needles (28%), m.p. 117-118", vnlau. (Nujol)1 770, 1450, 1 180, and 1040 cm-l, 6 4.66 (1 H, ddd, J 8.0,8.0, and 6.0 Hz, H-l), 3.7 (2 H, m, H-6 and -7), 3.03 (1 H, d,J 8.0 Hz, H-5), 2.7 (1 H, dd, J 15.0 and 8.0 Hz, H-8), 2.1(1 H, dd, J 15.0 and 6.0 Hz, H-8), and 2.06 (3 H, s, Me)(Found: C, 40.9; H, 3.9.C,H,BrO, requires C, 41.2;H, 3.8%).When the bicyclic ketone (2) was oxidised according tomethod B in the absence of sodium acetate, a mixture of thelactone (19) (25%) and 6-exo-brorno-2-exo-nzethyZ-4-oxatri-cy~Zo[3.2.1.0~~~]octan-3-one (22) (15%), b.p. 100-105' at0.01 mmHg, vmax. 1 730, 1 370, 1 230, and 1 110 cm-l, 6 4.5( 1 H, m, H-5), 4.2 (1 H, s, H-8), 2.49 (1 H, ddd, J 13.0, 3.0,and 3.0 Hz, H-61, 2.0 (3 H, m), and 1.25 (3 H,s, Me) (Found: A[+, 215.9786. C8HgBr0, requiresill, 215.9786), was obtained. The same lactone (22)was obtained by addition of NBA (1.4 g) t o asolution of the bicyclic ketone (2) (2 g) in acetone (3 ml)and water (15 ml). The mixture was left in the dark for10 h a t room temperature.The acetone was evaporated offand the residue was extracted with ether (3 x 20 ml).The combined extracts were washed with water (3 x 15 ml),dried, and evaporated. Distillation afforded compound(g) 4-endo-ChZo~o-4-exo-methyZ-2-oxabicycZo[3.3.0]oct-6-en-3-oize (20), from the bicyclic ketone (10) (method B; 90%acetic acid; 6 h a t 10 "C) was a liquid (75%), b.p. 97-100"a t 0.01 mmHg, vmax. 1 780, 1450, 1200, and 1 100 cm-l,6 5.8 (2 H, ni, H-6 and -7), 5.1 (1 H, m, H-1), 3.55 (1 H,m, H-6), 2.7 (2 H, m, 2 x H-8), and 1.8 (3 H, s, Me) (Found:M+, 172.0294.(h) 4-exo-Bvomo-4-endo-methyZ-2-oxabicyclo[3.3.O]oct-6-eiz-3-om (25), from the bicyclic ketone (1) (method B; 45 h)was an oil (34%), b.p.75-80' a t 0.01 mmHg, vmx. 1780,1 450, 1 180, and 1 070 cm-l, 6 5.75 (2 H, m, H-6 and -7),5.1 (1 H, m, H-l), 3.8 (1 H, m, H-5), 2.7 (2 H, m, 2 x H-8),and 1.9 (3 €3, s, Me) (Found: M+, 215.9786. C8HgBr02requires M , 215.9786).Whcn the oxidation was carried out by method A, thereaction was complete after 24 h and the lactone (25) wasobtaincd in 60% yield. In addition the endo-epoxy-Zactone(27) was isolated as an oil (16%), b.p. 110-114" a t 0.03mmHg, 6 5.0 (1 H, dd, J 6.0 and 6.0 Hz, H-l), 3.65 (2 H, m,H-6 and -7), 3.35 (1 H, dd, J 8.0 and 2.0 Hz, H-5), 2.48C,H,BrO, requires M , 215.9786).(22) (2.0 g, 92%).C,HgC102 requires M , 172.0290).(1 H, d, J 16.0 Hz, H-8), 2.15 (1 H, dd, J 16.0 and 6.0Hz, H-81, and 2.1 (3 H, s, Me) (Found: M', 231.9740.C,H,BrO, requires M , 231.9735).(i) 4-exo-Chloro-4-endo-methyZ-2-oxabicyc~o[3.3.O]oct-6-en-3-one (26), from the bicyclic ketone (9) (method B; 90%acetic acid; 16 h) was an oil (36y0), b.p.85-86O a t 0.02mmHg, vmx 1780, 1450, 1 190, and 1 110 cm-l, 6 5.7(2 H, m, H-6 and -7), 5.15 (1 H, m, H-l), 3.6 (1 H, m, H-5),2.7 (2 H, m, 2 x H-8), and 1.75 (3 H, s, Me) (Found: C,55.6; H, 5.4. C8H,C10, requires C, 55.8; H, 5.2%).When the oxidation was carried out in glacial acetic acid,the lactone (26) was obtained in 257; yield along with theendo-epoxy-Zactone (28) (8%) as an oil, vmx. (Nujol) 1770,1450, 1200, and 1100 cm-l, 8 4.9 (1 H, dd, J 6.0 and 6.0Hz, H-1), 3.5 (2 H, m, H-6 and -7), 3.14 (1 H, dd, J 6.0 andJ 15.0 and 7.0 Hz, H-8), and 1.9 (3 H, s, Me) (Found:C, 50.8; H, 4.6.CsH,C1O, requires C, 51.1; H, 4.8%).(j ) 4-exo-Bronzo-4-endo-isoproibyl-2-oxabic~clo[ 3.3.01 oct-6-en-3-one (29), from the bicyclic ketone (11) (method B;120 h) (6%) was an oil, v,, 1780, 1460, 1 190, and 1 170cm-1, 6 5.8 (2 H, m, H-6 and -7), 5.05 ( I H, m, H-1), 3.74(1 H, m, H-5), 2.7 (2 H, m, 2 x H-S), 1.85 (1 H, ni, H-9), and1.33 and 1.13 (6 H, 2 x d, J 6.0 Hz, 2 x Me), was obtainedalong with the endo-efloxy-Zactone (30), an oil (4%), 6 5.0(1 H, dd, J 6.0 and 6.0 Hz, H-l), 3.6 (2 H, ni, H-6 and -7),2.0 (1 H, dd, J 16.0 and 6.0 Hz, H-8), 2.1 ( 1 H, m, H-9).and 1.4 and 1.2 (6 H, 2 x d, J 6.0 Hz, 2 x Me) (Found:C, 46.3; H, 4.9.Dehydrohalogenation of the Bicyclic Lactones (14)-( 16),(18), (19), (25), and (29).-To a solution of the x-halogeno-lactone (0.001 mol) in dry toluene (10 ml) was added 1,5-diazabicyclo[4.3.0jnon-5-ene (DBN) (0.004 mol) and themixture was heated under reflux.When the reaction wascomplete, ether (20 ml) was added and the mixture waswashed with hydrochloric acid (10% ; 2 x 10 ml) and withsaturated sodium chloride solution (2 x 10 ml). The com-bined aqueous washings were extracted with ether (10 ml).The combined ether extracts were dried and evaporated.The products were purified by distillation or by preparativet.1.c.(a) 4-~ethy~ene-2-oxabiGyG~o[3.3.O]octan-3-one (3 l), fromthe lactone (14) (30 min) was an oil (75y0), b.p.95" at 0.08mmHg, vmx. 1 760, 1 665, 1 150, and 1 110 crn-l, 6 6.0 and5.55 (2 H, 2 x d, J 2.5 Hz, XH,), 4.85 (1 H, m, H-1), 3.4(1 H, m, H-5), and 1.7 (6 H, m) (Found: Mf, 138.0689.C8HloO2 requires M , 138.0681.)Treatment of the lactone (18) under the basic reactionconditions (24 h) also gave the lactone (31) (65%).(b) 9-Methylene-7-oxabicyclo[4.3.0]nonan-8-one (32) wasobtained (72%) from the lactone (16) after 30 min; b.p.75" a t 0.08 mmHg (lit.,13 60" at 0.06 mmHg), vmax. 1 7601 670, 1 450, and 1 130 cm-l, 6 6.02 and 5.47 (2 H, 3 x d,J 3 Hz, :CH2), 4.47 (1 H, m, H-6), 3.0 (1 H, m, H-1), and1.6 (8 H, m).(c) 4-MethyZene-2-oxabicyclo[3.3.0]oct-6-en-3-one (33) wasobtained from the lactone (25) as an oil (600,/,), b.p.80" a t0.08 mmHg, v,,,. 1 760, 1670, 1400, and 1 130 cm-1,6 6.0 and 5.53 (2 H, 2 x d, J 2.0 Hz, :CH,), 5.65 (2 H, m,H-6 and -7), 5.25 (1 H, m, H-l), 4.25 (1 H, m, H-5), and2.85 (2 H, m, 2 x H-8) (Found: M+, 136.0533. C,H802requires M , 136.0524).l3 J. A. Marshall and M. Cohen, J . Ovg. Chem.. 1965, 30, 3475.2.0 Hz, H-5), 2.5 (1 H, d, J 15.0 Hz, H-8), 2.05 (1 H, dd,3.25 (1 H, d, J 6.0 Hz, H-5), 2.55 (1 H, d, J 16.0 Hz, H-8).CloH1,BrO, requires C, 46.0; H, 5.0%)J.C.S. Perkin I(d) 4-IsopropyZidene-2-oxabicycZo[3.3.0]oct-6-en-3-one (34)was obtained from the lactone (29) as an oil (75%), b.p. 90"a t 0.08 mmHg, vmx. 1 735, 1 660, 1 180, and 1065 cm-l,6 5.6 (2 H, m, H-6 and - 7 ) , 4.85 (1 H, m, H-l), 3.9 (1 H, m,H-5), 2.7 (2 H, m, 2 x H-8), and 2.2 and 2.0 (6 H, 2 x s,2 x Me) (Found: Mi, 164.0845. CloHl,O, requires M ,164.0837).(e) 4-MethyZ-2-oxabicycZo[3.3.0]oct-4-e~-3-one (35) wasobtained from the lactone (15) as an oil (78%), b.p. 90" at0.08 mmHg, vmx. 1 750, 1 690, 1 450, and 1 130 cm-l,64.75 (1 H, m, H-l), 2.2 (6H, in), and 1.7 (3H, s, Me) (Found:Mf, 138.0682.(f) 4-Methyl-2-oxabicycZo[3.3.0]octa-4,8-dien-3-one (36),from the reaction of DBN with the lactone (19), was a semi-solid (80%), vmX. (CHCl,), 1760, 1660, and 1000 cm-l,6 5.6 (1 H, t, J 2.0 Hz, H-8), 2.8 (4 H, m), and 1.9 (3 H, s,Me) (Found: Mi, 136.0525. C,H,O, requires iWT, 136.0524).We thank the S.R.C. for financial support (to S. &M. A.).C,HloO, requires M , 138.0680).i6/352 Received, 19th February, 1976
ISSN:1472-7781
DOI:10.1039/P19760001934
出版商:RSC
年代:1976
数据来源: RSC