Regioselective Synthesis of Thiazole‐5‐thione Based on [2+3] Annulation Trapping of <i>α</i>‐Keto Sulfine with Thioamide

Abstract Aiming to develop novel annulation reactions using sulfine intermediates, we have established a regioselective formal [2+3] cyclization reaction of α ‐keto sulfines generated from the elimination of arylacyl sulfoxides and thioamides. This new strategy allows for the synthesis of thiazole‐5‐thiones directly without catalysts or additives. The approach features a step‐economic, one‐pot characteristics via a tandem sequence of in situ α ‐keto sulfines generation, regiospecifically nucleophilic attack or [3+2] cyclizatoin, dithioate (S=C−S−) skeletons formation, and subsequent intramolecular nucleophilic cyclization. This reaction also represents a novel method for constructing dithioate (S=C−S−) skeletons.