Selective alkylation of allyl phenyl sulphone. A novel synthesis of alk-2-enes

摘要

1977 123Selective Alkylation of Allyl Phenyl Sulphone. A Novel Synthesis ofAl k-2-enesBy Diego Savoia, Claudio Trombini, and Achille Umani-Ronchi, lstituto Chimico ' G Ciamician,' Unversita diTreatment of the lithium salt of allyl phenyl sulphone (1 ) with a variety of alkyl halides affords exclusively a-alkylatedproducts (2a-d). which are easily isomerized to (euro;)-ap-unsaturated phenyl sulphones (4a-d) with catalyticamounts of t-butoxide. A new, simple method of reductive cleavage of the carbon-sulphur bonds of compounds(2)-(4) with potassium-graphite (C,K) is described, providing a general route to alk-2-enes (5) and (6) insatisfactory yields.Bologna, via Selmi 2, 40126 Bologna, ItalyWE recently developed two general methods for thesynthesis of ap-unsaturated sulphones.One involvesthe reaction of aa-dimetallo-sulphones with carbonylcompounds,l and the other phase-transfer-catalysedcondensation of sulphones with aldehydes in a two-phasesystem.2Sulphur-stabilized allylic anions of sulphides and sul-phoxides are assuming an increasingly important role insynthetic chemistry, since they represent useful reagentsfor extending a carbon chain. In fact, allyl sulphidesand sulphoxides are readily a- and 7-alkylated, therelative amounts of products being system-de~endent.~No examples are reported of regioselective alkylationof allyl sulphoxides, but isopropylthioallylcopper andvinylthioallyl-lithium 5 are known to undergo exclusiveattack at the positions y and a to sulphur, respectively.We have now found that a novel stereospecific synthe-sis of ap-unsaturated sulphones may be accomplishedfrom the lithium salt of allyl phenyl sulphone (1).Allylphenyl sulphone is easily metallated with n-butyl-lithium in t e trahydrofuran-tetrame thyle t hylenediamineat -60 OC, and the product (1) is regioselectively alkyl-ated by alkyl halides in the =-position to give By-un-iaturated sulphones (2) as major product, with smallamounts of dialkylated sulphones (3).Upon treatment with catalytic amounts of potassiumt-butoxide in dry tetrahydrofuran at 0 "C, the pr-un-saturated sulphones (2) are converted completely intothe ap-unsaturated sulphones (4), with the E configura-tion, as demonstrated by the chemical shifts of vinylicand methyl protons in their n.m.r.spectra. In fact theisomers (4) show the vinylic proton signal at 6 7.0 andthat of the methyl protons at 6 1.euro;LSap-Unsaturated sulphones can be reductively cleavedto the corresponding alkenes by treatment with a reagentsuch as aluminium amalgam 'p8 or lithium-ethylamine,Qthe overall alkylation-desulphuration process providinga useful route to-olefins from sulphones. We thereforecarried out a series of experiments in order to establishV. Pascali, N. Tangari, and A. Umani-Ronchi, J.C.S.Perkin I , 1973, 441; A. Bongini, D. Savoia, and A. Umani-Ronchi, J . Organometallic Chem., 1976, 112, 1.G. Cardillo, D. Savoia, and A. Umani-Ronchi, Synthesis,1975, 463.D. A. Evans and G. C. Andrews, Accounts Chem. Res., 1974,7,147.K.Oshima, H. Yamamoto, and H. Nozaki, J . Amer. Chem.Soc., 1973, 95, 7926.K. Oshima, H. Takahashi, H. Yamamoto, and H. Nozaki,J . Amer. Chem. SOC., 1973, 95, 2693.whether these methods could be applied to our sulphones(2) and (4). In fact alk-2-enes (5) were obtained in satis-factory yields by usingperature (method A).aluminium amalgam.Better results underlithium-ethylamine at low tem-No reaction was observed withR W r R'(6 ItRCH=CHMe RY PhSO2 I51( 4 1SCHEMEmilder reaction conditions havebeen achieved by the use in dry diethyl ether at roomtemperature of potassium-graphite,lO an easily pre-pared new solid state reagent (method B). Results aresummarized in the Table. The reaction seems quitegeneral, leading in good yield to the expected alk-2-enes(5) in all cases studied.Cleavage of 3-phenylsulphonylundec- 1-ene (2b) byMethod B did not afford undec-1-ene, but the correspond-ing alk-2-ene (5b).The same rearrangement of thedouble bond was also observed in the reduction of 3-octyl-3-phenylsulphonylundec-1 -ene (3b).C. Y. Meyers and I. Sataty, Tetrahedron Letters, 1972, 42,4323.E. J. Corey and M. Chaykovsky, J . Amer. Chem. Soc., 1966,87, 1345. * V. Pascali and A. Umani-Ronchi, J.C.S. Chem. Comm., 1973,361.@ J. F. Biellmann and J. B. Ducep. Tetrahedron, 1971, 27,6861.lo J. M. Lalancette, G. Rollin, andP. Dumas, Canad. J . Chem.,1972, 50, 3068; H. Podall and W. E. Foster, J . Org. Chem., 1968,28, 401124 J.C.S. Perkin IHowever all desulphuration methods have the dis-advantage of inducing partial ZE-isomerization.Theratio of 2 to E-isomers is temperature-dependent, the E-isomer being the major product.Cleavage of sulphones ; synthesis of alk-2-enesStarting Yieldsulphone Method Alkene (yo)b Z:ERatioCB Undec-2-ene 77 35 : 65B 3-Octylundec-2-ene 81A Hept-2-ene 60 40 : 60B Hept-2-ene 61 30: 70A Undec-2-ene 62 40 : 60B Undec-2-ene 65 35 : 65B d Undec-2-ene 55 65 : 35A Nonadec-2-ene 65 45 : 55B Nonadec-2-ene 55 35 : 65A 1-Phenylbut-2-ene 24 46 : 65B l-Phenylbut-2-ene 26 40 : 60(2b)(3b)(44(4a)(4b)(4b)(4b)(4c)(4c)(44(4d)@ See Experimental section. Of pure isolated compounds;the yield of hept-2-ene was determined by g.1.c. with an internalstandard.c Z : E Ratio determined by g.1.c. on a Carbo-wax 20M column (+ in x 6 f t ; 10 on 80-100 meshChromosorb G) (W. E. Falconer and L. G. Walker, J . Chromatog.Sci., 1971.9,184). d This reaction was performed with lithium-methylamine at -110 "C for 10 min.When performing the cleavage with (E)S-phenyl-sulphonylundec-2-ene (4b) and lithium-methylamine at-110 O C , we observed the greatest retention of confipr-ation in the alkene (2 : E ratio 65 : 35) ; when the reactionis conducted at room temperature with potassium-graphite the ratio is inverted.EXPERIMENTAL1.r. spectra were determined with a double-beam LeitzSpectrograph, n.m.r. spectra with a Perkin-Elmer R12Binstrument (solvent CDCl,; Me,Si as internal standard), andmass spectra with a Hitachi-Perkin-Elmer RMU6D (singlefocus) spectrometer (at 70 eV).T.1.c. was performed onsilica gel H3?254 (Merck) and column chromatography onMerck silica gel (0.05-0.20 mesh) with hexane-ether as asolvent. Tetrahydrofuran was obtained dry and oxygen-free by distillation over sodium and lithium aluminiumhydride under argon. Tetramethylethylenediamine wasdistilled from calcium hydride under argon. n-Butyl-lithium was purchased from Schuchardt (Munchen) as a1.8~-solution in n-heptane. Graphite was used as suppliedfrom Carlo Erba, and contained 99 carbon.Alkylation of Ally1 Phenyl Sulphone.--In a three-neckedflask equipped with stirrer and dropping funnel, dry tetra-hydrofuran (50 ml) , tetramethylethylenediamine (3.05ml, 20 mmol), and ally1 phenyl sulphone (3.65 g, 20 mmol)were placed under argon.To the stirred solution n-butyl-lithium ( 1 . 8 ~ ; 11.2 ml, 20 mmol) was added over 15 min a t-60 "C. After 1 h the allryl halide (20 mmol) was addedand stirring continued a t - 60 "C for 3 h. The temperaturewas raised to 0 "C, then the mixture was poured into ice-water and extracted with ether. After washing with water,drying, and evaporating, the products were isolated bychromatography on silica gel.3-PhenyZsulphonylhe~t- 1-ene (2a) (78) had m.p. 46" (fromhexane); 6 7.5-8.1 (aromatic, m), 4.8-6.1 (vinylic, m),3.5 (SO,CH, dt), and 0.8-2.3 (aliphatic, m) ; M+ 238 (Found:C, 65.5; H, 7.5; S, 13.2. C,,H,,O,S requires C, 65.5; H,7.6; S, 13.4). 3-Phenylsulphonylundec-l-ene (2b) (71)had m.p.71" (from hexane); 6 7.5-8.1 (aromatic, m), 4.8-6.1 (vinylic, m), 3.5 (SO,CH, dt), and 0.8-2.2 (aliphatic, m);M+ 294 (Found: C , 69.1; H, 8.8; S, 10.9. C,,H,,02S re-quires C, 69.4; H, 8.9; S, 10.9). 3-Phenylsulphonyl-nonadec-l-ene (2c) (70) had m.p. 91" (from benzene);6 7.5-8.1 (aromatic, m), 4.8-6.1 (vinylic, m), 3.5 (SO,CH,dt), and 0.8-2.3 (aliphatic, m) ; M+ 406 (Found: C, 73.9;H, 10.4; S, 7.8. C,,H,,O,S requires C, 73.8; H, 10.4; S7.9). 3-Benzyl-3-~henylsul~honyl~ro~- l-ene (2d) (75)had m.p. 85" (from hexane-benzene); 6 7.5-8.1 (C,H,SO,,m), 7.2 (C6H5*CH,, m,), 4.6-6.1 (vinylic, m), and 2.6-4.0(CH,*CH, m); M+ 272 (Found: C, 70.6; H, 5.9; S, 11.8.C,,H,,O,S requires C, 70.6; H, 5.9; S, 11.7). 3-ButyZ-3-phenyZsul;6honylhe~t-l-ene (3a) (9) had m.p.78" (fromhexane) ; 6 7.4-8.0 (aromatic, m), 4.8-6.1 (vinylic, m), and0.8-2.2 (aliphatic, m); Mf 294 (Found: C, 69.6; H, 8.8;S, 10.6. C,,H2,0,S requires C, 69.4; H, 8.9; S, 10.9). 3-Octyl-3-~henylsul~honylundec- 1-ene (3b) (8) was an oil; 67.4-8.0 (aromatic, m), 4.8-6.1 (vinylic, m), and 0.8-2.2(aliphatic, m); M+ 406 (Found: C, 73.5; euro;3, 10.2; S, 7.7.C,,H,,O,S requires C, 73.8; H, 10.4; S, 7.9). 3-Hexa-decyl-3-phenylsulphonylnonadec- l-ene (3c) (6) had m.p.53" (from hexane) ; 6 7.4-8.0 (aromatic, m), 4.8-6.1 (viny-lic, m), and 0.8-2.2 (aliphatic, m); M+ 630 (Found: C,78.1; H, 11.3; S,5.0. C,,H,,O,SrequiresC, 78.0; H, 11.8;S, 5.1). 3,3-Dibenzyl-3-~henylsul~honyl~rop-l-ene (3d)(8) had m.p. 113" (from ether); 6 7.4-8.0 (C,H,SO,, m),7.2 (C,H,*CH,, m), 5.0-6.3 (vinylic, m), and 3.4 (CH,, s);M+ 362 (Found: C , 76.0; H, 6.0; S, 8.5.C,,H,,02S re-quires C , 76.2; H, 6.1; S, 8.8).Conversion of By- into a@- Unsaturated Su1phones.-Potas-sium t-butoxide (56 mg, 0.5 mmol) was added to a stirredsolution of py-unsaturated sulphone (2) (10 mmol) . in drytetrahydrofuran (20 ml). The mixture was stirred for 3 h,then added to saturated aqueous sodium chloride and extrac-ted with ether. The dried organic layer was evaporatedin vacuo. The a@-unsaturated sulphone was isolated afterchromatography on a silica gel column (hexane-ether,98 : 2).(E)-3-Phenylsulfiho.nylhept-2-ene (4a) (95) was an oil, 67.4-8.1 (aromatic, m), 7.0 (vinylic, q), 1.8 (H*CH,, d), and0.8-2.4 (aliphatic, m) ; M+ 238.(E)-3-Phenylsulphonyl-undec-2-ene (4b) (96) was an oil; 6 7.4-8.0 (aromatic, m),7.0 (vinylic, q), 1.8 (=CH*CH,, d), and 0.8-2.4 (aliphatic,m) ; M+ 294. (E)-3-Phenylsulphonylnonadec-2-ene (4c)(94) had m.p. 43" (from hexane) ; 6 7.4-8.0 (aromatic, m),7.0 (vinylic, q), 1.8 (H*CH,, d), and 0.8-2.4 (aliphatic,m) ; M+ 406. (E) - 1 -Benzyl- l-~henylsul~honyZpro~-2-ene(4d) (95) had m.p. 76" (from hexane-benzene); 6 7.3-7.9(C,H,*SO,, m), 7.2 (vinylic, q), 7.1 (C,H,CH,, m), 3.7 (CH,,s), and 1.8 (CH,, d); M+ 272.By lithium-ethyla-mine. General procedure. Dry ethylamine (20 ml) wascondensed in a three-necked flask equipped with stirrer andcold finger. Lithium (0.25 g, 45 mg atom), previouslywashed with pentane, was added over 10 min to the stirredamine.After the lithium had completely dissolved, thesulphone (4) ( 5 mmol) in dry ether (5 ml) was added a t -30"C. After 1 h the mixture was quenched with solid ammon-ium chloride and then allowed to rise to room temperature inorder t o remove most of the amine. After 30 min water(10 ml) was added and the mixture extracted with ether.Alk-2-enes were isolated as previously r e p ~ r t e d . ~A single reaction was carried out with lithium-methyl-amine at - 110 "C on the sulphone (4b) dissolved in meth-Cleavage of Sulphones.-Method A .anol1977 125Method B. By potassium-graphite (C,K) . General pro-cedwe. A three-necked flask was flushed with argon andheated with a flame, then charged with graphite (6.0 g, 0.5niol) and flamed again under argon in order to desorb anyoxygen and water from the graphite.A stirrer was thenintroduced and the system heated a t 100 "C (oil-bath).Potassium (2.42 g, 62 mg atom), previously washed with n-pentane, was added in small portions over 10 min withstirring, a bronze-coloured solid being obtained. The sul-phone (5 mmol) in dry ether or dry tetrahydrofuran (20 ml)was added dropwise to the potassium-graphite a t room tem-perature. After 1 h ice and ether were added, graphite wasfiltered off , and the organic phase was separated and evapor-ated. The residue was chromatographed on silica gel (15cm column, 1.7 cm diam.; elution with 50 ml of n-pentane)to give the alk-2-eneJ identified by i.r., n.m.r., and massspectral data, or by comparison with an authentic sample;hept-2-eneJ M+ 98; undec-2-ene, M+ 154, vmx. (film) 695(CHH-cis) l1 and 965 cm-l (CH=CH-trans), 8 (CCl,) 5.2-5.6 (vinylic, m); nonadec-2-eneJ M+ 266, vmx. (film) 700(CH=CH-cis) and 960 cm-l (CH=CH-trans), 8 (CCl,) 5.2-5.7(vinylic, m) : 3-octylundec-2-ene, M+ 266, vmx. (film) 845,970, 1015, and 1060 cm-l, 8 (CCl,) 5.3-5.6 (vinylic, m).This work was supported by a grant from the C.N.R.,Rome.6/1258 ReceivJ, 29th June, 19761l1 F. Naif and P. Degen, HeZv. Chim. Acta, 1971, 54, 1939