Coupling constants thiazole derivatives

NMR study of nitrothiazoles has been the subject of few number of works [525, 530-540], The proton chemical shifts of about 30 thiazole derivatives including 5-nitrothiazole and 2-nitrothiazole are presented in [536], The authors have found the coupling constants between H-2 and II-4 in most 5-substituted thiazoles to be negligible with the exception of 5-nitrothiazole and 5-thiazolecarboxylic acids [536], The change in the H-4 chemical shifts of the 2-substituted 5-nitrothiazole fragment enables the ratio of isomeric products of the reaction of 5-nitrothiazole 2-(T,3 -dicarbonyl) derivatives with hydrazine and hydroxylamine to be established (Scheme 3.8) [537],... 

TABLE 1-39. COUPLING CONSTANTS Jch (Hz) IN THIAZOLE AND SOME OF ITS DERIVATIVES A. Jc-H Couplings... 

Conformational analysis of 1,3-thiazolidines and other thiazole derivatives has been carried out by NMR methods (see Section 3.06.3.6.1). Thus, the analysis of the coupling constants of the H NMR spectra <74JA1465> permitted to postulate envelopes with either C-4 or C-5 as the flap atom and with the 2-substituent anti to the flap as the predominant conformations (Equation (2)). 

The natural abundance C chemical shifts for thiazole (and its 2-, 4-, 2,4-, and 4,5-methyl derivatives) have been measured at 25.15 MHz against 50% enriched 82. The results confirm the accuracy of the C-H coupling constants, and show that the methyl groups exert an appreciable substituent effect on the carbon atoms to which they are attached. 2-Thiazoline (and its 2-methyl, 5-methyl, and 5-methyl-2-ethyl homologues) have also been studied from this point of view. ... 

A detailed study of n.m.r. spectra has provided extensive data on chemical shifts and coupling constants in respect of a series of monophenyl-thiazoles, and their derivatives bearing alkyl and functional substituents in their hetero-rings. The chemical shifts were correlated with the net from electron density and energy diagrams, and the overall results were compared with those previously obtained in respect of thiazole and its methyl derivatives. 

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