Reactions of sulfenamides with alkynes in the presence of phosphorus(v) oxohalides

The reactions of alkynes with arylsulfenamides activated with phosphorus ox ohalides giving rise to aryl beta -halovinyl sulfides were investigated. Th e reactions with acetylene, oct-1-yne, and oct-4-yne are trans-stereospecif ic, whereas the reaction with phenylacetylene afforded a mixture of cis- an d trans-addition products. The addition to unsymmetrical alkynes yielded a mixture of Markovnikoff and anti-Markovnikoff isomers whose ratio depends o n the solvent. Products of addition to oct-1-yne in the presence of catalyt ic amounts of acids underwent isomerization.