Reactions of amines with β-(phenylseleninyl)vinyl sulfones derived from the selenosulfonation of acetylenes. Formation of enamine sulfones

Abstract

β-(Phenylseleno)vinyl sulfones 2 were prepared from the selenosulfonation of acetylenes and were oxidized to the corresponding selenoxides 3. These were treated insitu with morpholine (4) or pyrrolidine (5) to afford the corresponding enamine sulfones 6 and, in those cases where 3 were derived from terminal acetylenes, their selenenylated analogues 7. The formation of the latter was enhanced by adding benzeneselenenyl chloride to the reaction mixture, and suppressed by the presence of selenenic acid scavengers such as enamine 10 or ethyl vinyl ether. In several instances the enamine sulfones were hydrolyzed to β-keto sulfones prior to work-up. A mechanistic rationale for the formation of 6 and 7 is presented. Selenoxide 3f behaved anomalously when treated with pyrrolidine and underwent isomerization to an allyl selenoxide, followed by [2,3] sigmatropic rearrangement to produce allyl alcohol 18. Selenoxide 3f was reduced by N,N-dimethylhydrazine to the selenide 2f.