BF 3  ⋅ OEt 2 Catalyzed Synthesis of 1,3‐Thiazines/‐Selenazines

An efficient strategy for the synthesis of 3,4‐dihydro‐2 H ‐1,3‐thiazines / 3,4‐dihydro‐2 H ‐1,3‐selenazines from propargylic alcohols and thioamides/thiosemicarbazones/selenamides is described. The reaction is accomplished in moderate to excellent yield under mild conditions that did not require the exclusion of air or moisture and offers an operationally simplistic and convenient route to the synthetically useful six‐membered N,S/Se‐heterocycles.