Thiazoles, Isothiazoles, and Selenazoles

Trinajstic et al. have concluded from EHT calculations that the most probable conformation of 2-, 4-, and 5-phenylthiazoles (71) is a non-planar one and that the angle of twist about the inter-ring linkage increases in the order 4 2 5. The charge distribution for the energetically most favoured geometry was computed by the CNDO/2 method and the calculated dipole moments were found to be consistent with observed values. (For a previous theoretical study of the dipole moments of phenyl-substituted thiazoles, see ref. 139). 

The stabilization energies of the donor-acceptor molecular complexes of thiazoles and phenylthiazoles with tetracyanoethylene have been estimated 

Parkas, and N. Trinajstid, Croat. Chem. Acta, 1971,43, 107 V. Galasso and N. 

The PCILO method is most suitable and yields results which agree very well with experimental findings. 

The cis-trans isomerization of 2-formylbenzothiazole (72c) has been studied by Minkin et al. in a manner similar to that for the thiophen analogues (72b) should exist predominantly as the O, S-cis isomer. A PPP study of the tautomerism of 2-phenylaminothiazole (72b) has predicted the amino-tautomer to be more stable than the imino-tautomer, a finding in agreement with available experimental data.  

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