Acid-Promoted Cleavage of 4,4-Bis(Alkylthio)But-3-en-2-One and Subsequent Thio-Michael Addition to α,β-Unsaturated Ketones

4,4-Bis(ethylthio)but-3-en-2-one 1a and 4,4-bis(benzylthio)but-3-en-2- one 1b have been investigated as non-thiolic and odorless thiol equivalents in thio-Michael addition. Promoted by acetyl chloride in methanol, the cleavage of compounds 1a and 1b commenced and the in-situ generated thiols underwent facile acid-catalyzed conjugate addition to α,β-unsaturated ketones 2 affording the corresponding β-keto sulfides 3 in good yields.