4-Thiazolecarboxylic acid, ethyl ester

Ethyl thiazole-4-carboxylate 4-Thiazolecarboxylic acid, ethyl ester (8,9), (14527-43-6)... 

Hydroxythiazole, from chloroacetaldehyde and ammonium thiocaibamate, 258 4-Hydroxy-2-thiazolecarboxylic acid ethyl ester, self condensation of, 294 synthesis of, from ethylcyanoacetate and ethylthioglycolate, 294 from thioamides and a-haloacids or esters, 294... 

The Claisen condensation of an aliphatic ester and a thiazolic ester gives after acidic hydrolysis a thiazolylketone (56). For example, the Claisen condensation of ethyl 4-methyl-5-thiazolecarboxylate with ethyl acetate followed by acid hydrolysis gives methyl 4-methyl-5-thiazolyl ketone in 16% yield. 

Imoto and co-workers have also studied the pA values of substituted thiazolecarboxylic acids and the alkaline hydrolysis of their ethyl esters, each in three relative positions (2-B-4-Y, 2-B-5-Y, and 5-II-2-Y). In the case of the pA values, the p-values are far from constant, varying from 0.83 to 2,35, This variation is likely to be due to the intervention of tautomeric equilibria and of hydrogen bonds. The /3-ratios for the three sets of ester hydrolyses are roughly constant (0,61-0.73), and, assuming that the introduction of two heteroatoms leads to cumulative (multiplicative) effects on the transmission, this result is of the same order of magnitude as the product of the and values discussed above, i.e. 1.0 and 0.6, respectively. The lowest value for the pA (0,83) for the 2-R-5-COOH series is also of the same order of magnitude. All the available reaction constants are summarized in Table VI. 

For activated esters, the problem of halting reduction at the aldehyde stage is similar to that faced in the reduction of carboxylic acids the aldehyde must be converted in situ into an electroinactive form. In one case, that of reduction of ethyl 2-thiazolecarboxylate [17], the strongly hydrated aldehyde may be obtained in about 70% yield ... 

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