NEW METHODS FOR THE HOMOLOGATION OF THIAZOLES AND OXAZOLES BY REGIOSPECIFIC LITHIATIONS OF THIAZOLE- AND OXAZOLE-CARBOXYLIC ACID DERIVATIVES.

Article abstract of DOI:10.1016/S0040-4039(00)95542-4

Dianions <(5) and (7)> are obtained by regiospecific lithiations of the parent thiazole- and oxazole-carboxylic acids; when the 2-position is blocked by a phenyl group, 4-(or 5-) methyl groups can be lithiated in thiazole- or oxazole-5(or 4-)carboxylic acids .Lithiations of the 2,5-dimethyl isomers <(13) and (16)> are not regiospecific while those of the corresponding N,N-diethylamides give exclusively the monoanions (14) and (17); all of these new intermediates react efficiently with a range of electrophiles.