Synthesis of 2,3-dihydropyrazolo[5,1-b]thiazoles via a tandem condensation sulfur-extrusion reaction

2,3-Dihydropyrazolo[5,1-b]thiazoles 3 are the first representatives of a heterocyclic system, which are conveniently prepared by heating 3-aminorhodanines 1 with ethyl 2-bromo-3,3-diethoxypropionate ( 2 ), via a tandem condensation-sulfur extrusion reaction.