2,4-Disubstituted Thiazoles by Regioselective Cross-Coupling or Bromine-Magnesium Exchange Reactions of 2,4-Dibromothiazole

Abstract

Cross-coupling reactions occur on 2,4-dibromothiazole preferentiallyat the more electron-deficient 2-position. This fact can be favorablyused to prepare 2-substituted 4-bromothiazoles, which serve as precursorsfor 2,4-disubstituted thiazoles. Protocols for regioselective Negishiand Stille cross-coupling reactions are provided. Alternatively,the title compound can be metalated in 2-position by a halogen-metalexchange reaction. As a supplement to the well-established bromine-lithiumexchange, the regioselective bromine-magnesium exchangereaction is presented.