Addition of 4-chlorobenzenesulphenyl chloride to 3-methylbut-1-yne, hex-1-yne, and phenylacetylene: isomerization and hydrolysis of the adducts

Abstract

The addition of (4-ClC₆H₄SCl, (2), to RCHCH, (1; R = Prⁱ, Buⁿ), gives (E)-4-ClC₆H₄(R) C = C(H) Cl, (E)-(3), and (E)-4-ClC₆H₄(H) CC (R) Cl, (E)-(4) in a fixed ratio; the addition to (1; R = Ph) gives regiospecifically (E)-(3; R = Ph) in ethyl acetate, but different proportions of (E)-(3) and (E)-(4)(R = Ph) in chloroform, sym-tetrachloroethane, and acetic acid. With an excess of the sulphenyl chloride (2), (E)-(3) and (E)-(4) isomerize to (Z)-(4)(same R). The sulphuric-acid catalysed hydrolysis of (E)-(3; R = Prⁱ,Buⁿ, Ph) gives α-chloroketones RCOCH₂Cl (5)(same R). The (E)-(4) isomers do not hydrolyse.