Efficient palladium(II)-catalyzed homocoupling of thiazole-4-carboxylic or oxazole-4-carboxylic derivatives
摘要:
An efficient Pd(OAc)(2)-catalyzed homocoupling of thiazole-4-carboxylic or oxazole-4-carboxylic derivatives is described. It represents a facile and practical methodology to prepare bis-5,5'-thiazole (oxazole)-4,4'-dicarboxylic derivatives in good to excellent yields. This protocol tolerates a series of substitutions on the thiazole (oxazole) rings, including alkyl, carbonyl, and electron-withdrawing/donating group substituted phenyl groups. (C) 2011 Elsevier Ltd. All rights reserved.
Dimethyl amino[(phenylthio)methyl]malonate: a useful C-3 unit in a mild, direct synthesis of oxazole-4-carboxylates
摘要:
N-Acyl derivatives of the title compound undergo oxidative cyclization upon treatment with N-chlorosuccinimide in DMF to form dimethyl 4,5-dihydro(phenylthio)oxazole-4,4-dicarboxylates 4 which then are decarbomethoxylated with concomitant loss of thiophenoxide to form 2-substituted-4-carbomethoxy-5-unsubstituted oxazoles 1. The mildness and generality of this method has been demonstrated by the synthesis of a variety of examples, including a fragment used for a synthesis of calyculin A.