Reaction of α, β -Unsaturated α-Chloro-β-amino Ketones with Thiols

Abstract

The reaction of α, β-unsaturated α-chloro-β-amino ketones with thiols was investigated and the structures of the products wereestablished. The reaction of 4-amino-3-chloro-3-penten-2-one [1], 3-amino-2-chloro-1-phenyl-2-buten-1-one [2] and 3-amino-2-chloro-1, 3-diphenyl-2-propen-1-one [3] with ethanethiol or p-substituted benzenethiols (substituent X : Me and NO2) in CCl4 under nitrogen atmosphere at room temperature gave 4-amino-3-ethylthio-3-penten-2-one [4a], 4-amino-3-p-substituted phenylthio-3-penten-2-one [5a], 3-amino-2-phenylthio-1-ptienyl-2-buten-1-one [8a] and 3-amino-2-phenylthio-1, 3-diphenyl-2-propen-1-one [9a], respeetively. The N-methyl and N-phenyl derivatives gave the corresponding products [4b], [5b, c], [6b], [7b], [8b, c] and [9b].
The effect of p-substitutent on nucleophilic reactivity of benzenethiols was elucidated. It was found that introduction of ethylthio or phenylthio group into α-position of enamino ketones resulted in a marked delocalization of π-electrons in the hydrogen bonded chelate ring. The enhanced stability of the chelate ring is rationalized in terms of the electron withdrawing resonance effect of S atom through pπ-dπ conjugation.