Elimination–addition. Part XIV. Addition of carboxylate ions to allenes and acetylenes and use of the adducts in acylation

Abstract

Base-catalysed additions of acetic, benzoic, and hippuric acids to propadienyl, prop-1-ynyl, and prop-2-ynyl p-tolyl sulphones and to ethynyl phenyl ketone occur readily under mild conditions. The products are 1-(aryl-sulphonylmethyl)vinyl or β-benzoylvinyl esters of the acids and as such are very reactive towards nucleophiles in acylation reactions.

Reactions of amines with the sulphonyl esters yield amides. Reactions of the keto-esters, however, involve either acylation or addition to the carbon–carbon double bond. The latter process regenerates the acid and occurs to an extent which depends upon the amine and upon the acid used. The adduct from benzoic acid and ethynyl phenyl ketone does not benzoylate amines but the acetate gives good yields of acetamides with primary amines although with secondary amines, mixtures of acid and amide or acid alone are obtained. Some acylamides are formed in good yield by addition of acid and triethylamine and then the amine to an acetylenic sulphone in dimethyl sulphoxide.

Reactions of the adducts with other nucleophiles have been briefly investigated. Acylations of phenol and methanol can be achieved; the latter reaction is carboxylate-ion catalysed, probably owing to the formation of an intermediate anhydride. Thiols give low yields of thiolesters.