Synthesis and highly diastereoselective nucleophilic epoxidation of N-(p-tolylsulfonyl)vinylsulfoximines

Abstract

N-(p-Tolylsulfonyl)vinylsulfoximines 3 may be prepared in good yield in a one-pot process by reaction of lithiated S-methyl-S-phenyl-N-(p-tolylsulfonyl)sulfoximine with aldehydes, followed by elimination using methanesulfonyl chloride-triethylamine. The vinylsulfoximines are formed as E-isomers with high selectivity. In one case, the stereochemistry of the double bond was confirmed by an X-ray crystal structure determination. Nucleophilic epoxidation of vinylsulfoximines using lithium tert-butyl peroxide in THF (tetrahydrofuran) occurs rapidly at low temperatures to give good yields of the corresponding sulfoximinooxiranes 5, with high diastereoselectivity. The sense of diastereoselectivity was established by an X-ray crystal structure determination. Vinylsulfoximines 3 may be deprotonated at the α-position and alkylated in fair yields. Epoxidation of these alkylated alkenes was much slower but nonetheless highly diastereoselective. The sense of diastereoselectivity was established to be the same as that in the case of α-unsubstituted examples by an X-ray crystal structure determination.