Synthesis of 1,3-Oxathiolan-5-ones and Benzoxathian-4-ones

Significance

An efficient synthesis of oxathiol­anone and benzoxathianone derivatives from the reaction of readily available trifluoroacetimidoyl chlorides with mercaptocarboxylic acids is reported. The ring size is critical for this reaction. Thus, although oxathiolanones are readily formed from α -mercaptocarboxylic acids and imidoyl chlorides, application of β-mercaptopropionic acids for this reaction leads to the formation of acyclic rather than cyclic products. However, use of thiosalicylic acid leads to the formation of the benzoxathia­nones, suggesting the requirement of a cis SH and OH arrangement for successful cyclization. The interesting part of this facile transformation is that the imine acts as a 1,1-electrophile without the nitrogen atom being integrated into the hetero­cyclic ring. The scope of the reaction requires exploration.