Nucleophilic sulfanylation of 1,5-disubstituted pent-2-en-4-yn-1-ones

Regioselectivity of nucleophilic addition of benzenethiols and phenylmethanethiol to 1,5-diarylpent-2-en-4-yn-1-ones in ethanol in the presence of triethylamine at 0–30°C is determined by the nucleophile nature. Phenylmethanethiol adds to the double bond, whereas benzenethiols add to the triple bond. The addition products, 1,5-diaryl-3-benzylsulfanylpent-4-yn-1-ones and 1,5-diaryl-5-(4-arylsulfanyl)penta-2,4-dien-1-ones, respectively, were isolated in 43–89% yield. Substituents in the aryl rings of the substrates did not affect the reaction direction.