Cytotoxic compounds. Part XX. Reactions of the methanesulphonates of 2-aryl-2-(arylthio)ethanols and of 1-aryl-2-(arylthio)ethanols with nucleophiles

Abstract

The products formed in the reactions of 2-phenyl-, 2-(p-methoxyphenyl)-, 2-(p-nitrophenyl)-, and 1-(p-nitrophenyl)-2-(phenylthio)ethyl methanesulphonate, 1-phenyl-2-(phenylthio)ethyl chloride, and 2-(2,4-dinitrophenylthio)-2-phenylethyl and -1-phenylethyl methanesulphonate with various nucleophiles have been identified, mainly by n.m.r. spectroscopy. Solvolysis in acetic acid or in methanol proceeds under kinetic control, via episulphonium ions, to give entirely the secondary acetate or secondary methyl ether. Reactions with potassium acetate, tetramethylammonium acetate, or sodium methoxide give vinyl sulphides from some of the substrates, particularly when an electron-attracting group is present at the β-position; with the acetate reagents, elimination occurs more readily in acetone than in acetic anhydride. Episulphonium intermediates are also involved in most of the reactions with lithium bromide, sodium azide, and arenethiols, to give substitution products, though with sodium azide the primary methanesulphonates carrying nitro-substituents give vinyl sulphides exclusively.

α-(Phenylthio)styrene and α-(phenylthio)-p-nitrostyrene are rapidly oxidised, with rearrangement, on exposure to air, to give phenacyl and p-nitrophenacyl phenyl sulphide, respectively.