Reactions of beta-keto sulfoxides with sulfur electrophiles. Part II. Stereochemical and configurational studies of the intermediate enolates

Some beta-keto sulfoxides containing different groups at the sulfinyl moiet y were submitted to sulfenylation reaction employing two procedures: in hom ogeneous media and by PTC to give the corresponding monosulfenylated produc ts. The Z configuration for the enolates of the P-keto sulfoxides independe ntly of the group at the sulfur moiety is proved by H-1 NMR NOE difference experiments. The diastereoselectivity observed in the case of a t-butyl sul finyl derivative is rationalized by preferred attack of the sulfur electrop hile to the unhindered face of enolate not shielded by t-butyl group, as sh own by X-ray analysis of the corresponding enol ether.