3- -Phenylthiazole, from irradiation

This symmetry is removed in the case of 2-deuterio-5-phenylthiazole 52-2d, and hence deuterium labeling expands the dyad into a tetrad. As expected from this analysis, irradiation of 2-deuterio-5-phenylthiazole 52-2d resulted in the formation of 4-deuterio-5-phenylthiazole 52-4d, the product of a Pg permutation process not observed in the absence of deuteration, and to 5-deuterio-4-phenylisothiazole 48-5d and 3-deuterio-4-phenylisothiazole 48-3d, formed via P5 and P7 pathways respectively. Again, these observations are entirely consistent with the electrocyclic ring closure heteroatom migration mechanism shown in Scheme 10. 

Reinvestigation of these reactions, however, gave substantially different results. Thus Pavlik and coworkers observed that 3-phenylisothiazole 47 is formed with deuterium incorporation at C-4 upon irradiation of either 2-phenylthiazole 50 or 5-phenylisothiazole 49 but with approximately twice the extent of incorporation from the latter reactant. Furthermore, although Maeda... 

The luminescence of the Eu(III) complex Eu(THlA)2(HFA)3 (THIA 4,5-bis (5-methyl-2-phenylthiazole) is efficiently quenched when the photochromic ligand THIA is converted from the colorless ring-open form to the closed-ring form upon UV light irradiation, resulting in change of the emission intensity [126]. 

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