Reactions of Ketone Hydrazones and β-Keto Enamines with Disulfur Dichloride. New Synthesis of Thioketones and 5H-1,2,3-Dithiazoles

Ketone hydrazones react with disulfur dichloride in the presence of triethylamine to afford thioketones in good yields. The reaction mechanism involving N-thiosulfinylamine (R2C=N–N=S=S) and S-thioxothioketone (R2C=S=S) is proposed. The formation of t-butyl and di-1-adamantyl thioketones even at low temperatures has been interpreted as steric congestion alone being not enough to stabilize the corresponding S-thioxothioketones. The reaction of β-ketoenamines with disulfur dichloride gives 5H-1,2,3-dithiazoles via intramolecular cyclization of intermediary N-thiosulfinylamines.