Synthesis of 2-(o-hydroxyaryl)-4-arylthiazoles by regioselective Pd(0)-catalyzed cross-coupling

The difunctional substrate 2,4-dibromothiazole 2 was transformed into the t itle compounds 1 by consecutive Pd(0)-catalyzed cross-coupling reactions. A ryl zinc reagents which were prepared by ortho-lithiation of compounds 3 an d subsequent transmetalation were used as carbon nucleophiles in the first coupling reaction. By this means, an aryl substituent was attached to the 2 -position (50-62% yield). A succeeding cross-coupling with arylboronic acid s 4 occurred at the 4-position of the intermediate 4-bromothiazoles 5 (76-9 7% yield). (C) 2000 Elsevier Science Ltd. All rights reserved.