ABSTRACT
Methylisothiazoles have been shown to undergo transposition. The photochemistry of pyrazoles and isothiazoles can be rationalized by a single unifying mechanistic scheme. The photoisomerization of isothiazole to thiazole was the first reported phototransposition in the isothiazole-thiazole heterocyclic system. G. Vemin and colleagues conducted extensive studies of the phototransposition chemistry of phenylisothiazoles and phenylthiazoles in benzene solution. James W. Pavlik and coworkers reinvestigated the phototransposition chemistry of cyclic compounds. A more significant difference between pyrazole and isothiazole photochemistry, however, appears to be the minor role of the poly4 pathway in isothiazole transposition. The interconversions within the tetrad are consistent with the electrocyclic ring closure heteroatom migration mechanistic pathway. Mounting evidence indicates that isocyanides are imortant intermediates on the P4 transposition pathway. Theoretical calculations led to the same conclusion in the case of-shifts of sulfur and oxygen in the phototransposition reactions of thiophene and oxazole respectively.
