Regioselectivity in the Lithiation of Methyl-substituted Thiazole- and Oxazole-Carboxylic Acids and Carboxamides: General Methods for the Elaboration of Trisubstituted Thiazoles and Oxazoles
A number of anionic intermediates have been developed which are suitable for the elaboration of trisubstituted thiazoles and oxazoles.Thus, deprotonation of 2,4-dimethylthiazole-5-carboxylic acid 9 using either BuLi or LDA occurs regiospecifically at the
Cornwall, Philip,Dell, Colin P.,Knight, David W.
p. 2417 - 2428
(2007/10/02)
NEW METHODS FOR THE HOMOLOGATION OF THIAZOLES AND OXAZOLES BY REGIOSPECIFIC LITHIATIONS OF THIAZOLE- AND OXAZOLE-CARBOXYLIC ACID DERIVATIVES.
Dianions 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 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.
Cornwall, Philip,Dell, Colin P.,Knight, David W.
p. 3585 - 3588
(2007/10/02)
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