TsNBr2 promoted cascade formation of C–N and C–S bond: Metal-free synthesis of 2-aminothiazoles from ketones or ketoximes using thiourea

Abstract

An efficient metal-free protocol for the synthesis of 2-aminothiazole via the C–N/C–S bond-forming reaction has been developed by treating ketones and thiourea with TsNBr2. The cascade reaction proceeds via the isolable α-bromoketone and α,α-dibromoketone intermediates in methanol at reflux temperature. Both aromatic and aliphatic ketones undergo oxidative cyclization with thiourea to give the desired product in high yield within a short reaction time. Additionally, we have also developed another strategy for the synthesis of 2-aminothiazole from ketoximes under the same optimized conditions using TsNBr2 and thiourea.