Thia-michael addition reactions using 2-[bis(alkylthio)methylene]-3-oxo-N-o-tolylbutanamides as odorless and efficient thiol equivalents

A series of 2-[bis(alkylthio)methylene]-3-oxo-N-o-tolylbutanamides 1 have been investigated as nonthiolic and odorless thiol equivalents in thia-Michael addition reactions. The cleavage of compounds 1 is initiated by NaOH in EtOH; the in situ generated thiolate anions undergo facile conjugate addition to alpha,beta-unsaturated carbonyl compounds 2 affording the corresponding beta-keto sulfides 3 in very high yields. Meanwhile, 3-oxo-N-o-tolylbutanamide 4, the precursor of compounds 1, can be recovered from the novel thia-Michael addition reactions as a byproduct in good yield.