Synthesis of Functionalized 2‐Hydrazono‐3‐Thiazolines from 2‐Substituted Oxazoles through a One‐Pot Multicomponent/Rearrangement Process

The serendipitous rearrangement of an oxazole nucleus to a thiazoline ring under mild conditions is described. This transformation was achieved by a multicomponent reaction (MCR) featuring 2‐(bromomethyl)oxazoles, thiosemicarbazide, and a carbonyl compound to provide oxazole‐derived isothiosemicarbazones, which undergo oxazole ring‐opening and recyclization to 2‐hydrazono‐3‐thiazolines in a one‐pot procedure. This straightforward route produced highly functionalized thiazolines (34–98 % yield) in a chemo‐ and stereoselective manner.