5- Thiazolecarboxylic acid methyl

As noted by Robinson and Strachan (1), after considerable activity in the period 1885 to 1895 thiazolecarboxylic acids received little attention until 1935. Isolation of 4-methyl-5-thiazolecarboxylic acid after degradation of vitamin Bj gave new interest to the chemistry of these compounds. 

On account of the high degree of stability of the thiazole ring a large variety of substituted derivatives yield thiazolecarboxylic acids upon oxidation. The oxidation of a methyl group or a substituted methyl group to a carboxyl group has been accomplished in a few instances. 

Ozonolysis of 2-styryl-4-methylthiazole followed by oxidation of the intermediate carbonyl compound with peracetic acid yields 4-methyl-2-thiazolecarboxylic acid (30). 

Hydrolysis of ethyl 4-methyl-2,5-thiazole dicarboxylate (9) or dicar-boxylic acid dichloride gives an excellent yield of 4-methyl-5 thiazole carboxylic acid (10) instead of the dicarboxylic acid (Scheme 6). This lability is a general Property of 2-thiazolecarboxylic acids. 

Some esters of substituted alcohols have been synthesized by transesterification. Treatment of 4-methyl-5-thiazolecarboxylic acid (14) with 3-chloroethyldiethylamine in acetone in the presence of anhydrous potassium carbonate gives the desired ester (15) in good vield (60%) (Scheme 10) (163). 

Boon has observed that when 2,4-dimethyl-5-thiazolecarboxylic acid (22) is heated with an excess of thionyl chloride, the main product (76%) is 4-methyl-2,5-thiazoledicarboxylic acid dichloride (23) (Scheme 14 (7). 

AOPCP, a, P-methylene-adenosine diphosphate APnA, diadenosine polyphosphate (n=3-6) ARL 67156,6-N,N-diethyl-D- 3,y-dibromomethylene ATP CMTA, 2-(3-cyano-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylic acid EHNA, erythro-9-(2-hydroxy-3-nonyl)adenine NBTI, nitrobenzylthioinosine. 

The nucleophilic reactivity in neutral medium has been used extensively to prepare various thioethers of thiazole (122). In acidic medium, alkylation may be performed with alcohols (123, 124). An unexpected reaction encountered was the decarboxylation of 2-mercapto-4-methyl-5-thiazolecarboxylic acid (60) when treated with butyl alcohol under acidic conditions (Scheme 27) (123). Reaction between A-4-thiazoline-2-thione... 

C5H5N02S 4-methyl-5-thiazolecarboxylic acid 20485-41-0 25.00 1.3382 2 4579 C5H604 trans-1,2-cyclopropanedicarboxylic acid, ( )- 58616-95-8 20.00 1.4600 1... 

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. 

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