STEREOSELECTIVE ADDITION OF ORGANOMETALLIC REAGENTS TO N-(TOSYL)VINYLSULFOXIMINES

Treatment of N-(toluene-p-sulfonyl)vinylsulfoximines 3 with methyllith ium at -78 degrees C, followed by addition of chlorotrimethylsilane, r esults in the efficient formation of alpha-silyl vinylsulfoximines 6 i n good to excellent yield, Nucleophilic addition of a range of simple alkyl and aryl organometallics (lithium, copper-lithium and Grignard r eagents) occurs in variable yield to give the Michael adducts 8, with organolithium reagents most effective, The degree of stereoselectivity of each of the addition reactions was determined by H-1 NMR of the de silylated products 9, and proved to be synthetically useful for compou nds in which the starting alpha-silylvinylsulfoximines were branched a t the gamma-position, and also when phenyllithium was used as the nucl eophile, The sense of stereoselectivity was determined in two cases by X-ray crystal structure analyses (of 9e and 9i), A one-pot process fo r the conversion of alpha-silylvinylsulfoximines 6 to alpha-substitute d carboxylic acids 11 was developed, using an in situ phenylselenation -oxidation process following the initial conjugate addition, Use of en antiomerically pure starting materials allowed the assignment of confi guration of two carboxylic acids (13e and 13h) by comparison with lite rature data, and hence indirectly of the relative stereochemistry of t he initial Michael adducts 9e and 9h.