Stereochemistry of Base-catalysed Addition of Methyl Mercaptoacetate to Acetylenic Ketones and Esters. Effects of Activating Groups and Solvents

Article abstract of DOI:10.1246/bcsj.53.1739

Piperidine-catalysed addition of methyl mercaptoacetate to benzoyl- and p-chlorobenzoyl-phenylacetylenes in ethanol gave the corresponding (Z)-1-aryl-3-(methoxycarbonylmethylthio)-3-phenyl-2-propen-1-one.However, p-anisoylphenylacetylene gave a mixture of (Z)- and (E)-3-(methoxycarbonylmethylthio)-1-(p-methoxyphenyl)-3-phenyl-2-propen-1-ones in the ratio of 4:1.This ratio was completely inverted when the latter addition was carried out in dry benzene.Rationalisation of these results is presented which depends on the effect of activating groups and solvents on thestereochemistry of addition.Piperidine-catalysed addition of methyl mercaptoacetate to methyl phenylpropiolate in ethanol gave methyl (Z)-3-(methoxycarbonylmethylthio)cinnamate.Hydrazine hydrate converted some of the above mono-adducts into some pyrazole derivatives.