P r e p a r a t i o n of Chiral (E)-1-Alkenyl Sulfoxides
J.Org. Chem., Vol. 43,No. 21, 1978 4131
stirred at room temperature for 1 h. The reaction mixture was filtered and the filtrate was evaporated on a rotary evaporator. The solid residue was chromatographed on a column of silica gel eluting with diethyl ether. Evaporation of the solvent afforded a deep violet solid which was crystallized from n-hexane to give deep violet crystals (50 mg, 30%), identical in all respects with an authentic sample of 13.
References and Notes
Acknowledgment. W e would like t o t h a n k t h e Ministry of Science a n d Higher Education for generous support of this work with G r a n t No. 600-1-36/1. Registry No.-?', 23308-83-0; 8, 42546-50-9; 9, 24234-76-2; loa, 59625-73-9; lob, 66809-63-0; 11, 66809-64-1; 12, 66809-65-2; 13, 66809-66-3; 14, 66809-78-7; 15, 66809-67-4; 16, 66809-68-5; 18, 52260-38-5; 19, 5471-63-6; 20, 66809-69-6; o-nitrobenzyl bromide, 3958-60-9;triphenylphosphine, 603-35-0.
(1) M. P. Cava, B. Hwang, and J. P. Van
Meter, J. Am. Chem. SOC.,65,4032 (1963). (2) M. P. Cava, H. Firouzabadi, and M. Krieger; J. Org. Chem., 39, 460 (1974). (3) P. J. Garratt, K . Peter, and C. Vollhardt, J. Am. Chem. Soc., 94, 1022 (1972). (4) H. Straub, Angew. Chem., Int. Ed. Engl., 13, 405 (1974). (5) (a) F. Toda and M. Ohi, J. Chem. SOC.,Chem. Commun., 506 (1975);(b) F. Toda and N. Dam: ibid., 30 (1976). (6) A. T. Blomquist and E. A. LaLancette, J. Am. Chem. Soc., 63, 1387 (1961). (7) J. M. Landesberg, L. Katz, and J. Olson, J. Org. Chem., 37, 930 (1972). (6) Spectrum No. 305, Varian Associates NMR Spectra Catalogue. (9) M. Wilk, H. Schwab, and J. Rochlitz, Justus Liebigs Ann. Chem., 698, 149 (1966). (IO) Huebel and Barge have observed the formation of the Same kind of product on heating diphenylacetylene with triiron dodecacarbonyl:W . Huebel and E. H. Barge, J. Nucl. Inorg. Chem., 10, 250 (1959). (11) Although compound 7 has been generated previously, its isolation and characterization have not been described: G. P. Schiementz, J. Becker. and J. Stoekigt, Chem. Ber., 103, 2077 (1970).
Stereocontrolled Preparation of Chiral (E)-1-AlkenylSulfoxides. Efficient Reduction of Alkenyl Sulfoxides to the Corresponding Alkenyl Sulfides Gary H. Posner* a n d P i n g - W a h T a n g D e p a r t m e n t of Chemzstry, T h e Johns Hopklns C n i c e r s z t j , Baltimore, Maryland 21218 Recezoed M a ) 8, 1978 (E)-1-Alkenylmagnesiumbromides react cleanly and stereospecifically with chiral menthyl sulfinate esters to produce chiral (E)-1-alkenyl sulfoxides; no alkenyl sulfide is formed in this process. 1-Alkenyl and 2-alkenyl aryl sulfoxides are easily reduced to the corresponding vinylic sulfides upon treatment with ethylmagnesium bromide/ 10% cuprous iodide at 0 "C for 1 h. No double bond isomerization occurs during this sulfoxide deoxygenation, and 1,3-butadienylsulfoxides are reduced cleanly to 1,3-butadienyl sulfides. Proton NMR indicates an upfield chemical shift of about 0.1 and 0.6 ppm for H, and Hp in the a,$-ethylenic sulfides relative to the corresponding sulfoxides P u r s u i n g our interest in reactions of organometallic reagents with a$-unsaturated sulfur compounds,' we have sought a stereocontrolled m e t h o d for preparing either (2)1-alkenyl or (E)-1-alkenyl sulfoxides. T h e Carey-Hernandez synthesis using carbonyl compounds a n d 1-(trimethylsily1)1-(phenylsulfiny1)methyllithiumleads t o a mixture of (2)and (E)-vinylic sulfoxides,2 a n d t h e Horner-Wittig procedure using carbonyl compounds a n d sulfinyl methylphosphonate anions also leads t o a mixture of geometrical isomers in which t h e E isomer often predominate^.^ Separation of vinylic sulfoxide geometrical isomers is often difficult a n d t i m e consuming, a n d t h e overall yields of p u r e E or 2 isomers a r e usually l 0 w . ~ 3W~ e report here our recent success in stereo-
R
I
2. Br,
SOR
i H EtMgBr
(23)
SOPh
10%CUI
EtMgBr
SPh
R (2b) SPh
specifically converting (E)-vinylic bromides via t h e corresponding Grignard reagents into ( E )-vinylic sulfoxides in good and yields via eq 1. W e report also our discovery t h a t (2)(E)-vinylic phenyl sulfoxides a r e easily reduced b y ethylmagnesium bromide/lO% cuprous iodide with retention of double bond configuration t o t h e corresponding (2)and (E)-vinylic phenyl sulfides under mild conditions a n d in high yields (eq 2).
Results and Discussion Preparation of (E)-1-Alkenyl Sulfoxides. Reaction of Grignard reagents with chiral sulfinate esters is one of t h e oldest a n d most often used procedures for preparation of chiral sulfoxide^.^ H a r p p has recently summarized t h i s area a n d has emphasized that a major byproduct in t h i s t y p e of reaction is often t h e sulfide derived from t h e initially formed s ~ l f o x i d e .H~a r p p recommends general use of organocopperlithium reagents for conversion of sulfinate esters into t h e corresponding sulfoxides with formation usually of only small a m o u n t s of sulfides. W e have found t h a t menthyl p - t o l u e n esulfinate reacts with isopropenylmagnesium bromide/lO% cuprous iodide t o give substantial (e.g., 30-40%) a m o u n t s of sulfide. Surprisingly, however, we have found t h a t vinylic Grignard reagents in t h e absence of a n y copper salts react cleanly with m e n t h y l sulfinate esters in tetrahydrofuran t o give only t h e corresponding vinylic sulfoxides a n d n o detectable a m o u n t s of vinylic sulfides as indicated b y t h e comparison with a u t h e n t i c sulfides ( T a b l e I).
0022-326317811943-4131$01.00/0 0 1978 American Chemical Society
4132
J . Org. C'hem., Vol. 43, No. 21, 1978
Posner and Tang
Table I. Reaction of (-)-Menthyl (-)-(S)-Sulfinate Esters with Vinylic Grignard Reagents in Tetrahydrofuran menthyl-OS(0)R' (1 equiv),
R' = p-tolyl
%) yield
of
registry no. 1517-82-4
p-tolyl
Grignard
time,
temp,
(1.3 equiv)
h
O C
CH?=C(CH:JMgBr
20
(E)-CeIII,= , j 15.6)" 6.58, 6.71 (Jcv,d= 16) 6.44 ( H ( ? )6.64-6.90 , ( m , 3 H , vinyl HIa 6.30-6.88 (m, 4 H, vinyl H ) 1.52-1.60 (m, 6 H, Me&=), 1.88 (s, 3 H, 1.76 (s, 3 H, C4-Me),5.0 (br s, Cj-H), 5.80 Cd-Me), 5.02-5.20 ( m , Cy-H), 5.88 id, (d, C3-H, 5 2 - 3 = 10.8),6.10 (d, CI-H, J 1 . 2 = 14.4), 6.54 (d of d , C2-H) C:j-H,Jn-:i = 11.3),6.20 (d, C I - H , J1-2 = 14.3), 7.16 (d of d , C2-H) 5.98 (s, Ho) 5.88 (s, H(t) 1.55 (s, vinyl Me) 1.95 (s, vinyl Me) 0.69 (s, Cls-Me),0.83 (s, Cly-Me), 5.78 0.68 (s, Cla-Me), 0.83 (s, CIg-Me), 5.70 (s,H,,)," 6.68 (s,C4-H)' (s, H c v ) ,6.28 f (s,C4-H)f
mle ( M + ) 206
212
238 258
CDCl:+ M p 80 "C; m/e 254 (M+);sulfide mp 72-73 "C. Spectral data recorded only for the mixture of geometrical ( E ) - l ,W - 3 and (E)-l,( E ) - 31,3,7-nonatriene isomers. Mp 168-169 "C. Anal. Calcd for C3hH540S: C, 80.40; H , 10.41; S, 6.13. Found: C, 80.06; H, 10.19; S,6.39. Sulfide m p 138.5-139.5 "C. Anal. Calcd for C35H54S: C, 82.94; H , 10.65; S, 6.32. Found: C, 83.03; H , 10.69; S, 6.24. T h e minor geometrical isomer had b 5.94 (s, H
