Azines and azoles. 64. Mass spectra and tautomerism of 2-aryl-4,6-dioxo-1,3-thiazines

Mass spectra of 2-aryl-4,6-dioxo-1,3-thiazines were studied and the general fragmentation paths of these compounds determined. Based on mass spectra of compounds with fixed structures, 2-aryl-5,5-dialkyl-4,6-dioxo-1,3-thiazines, 4-alkoxy- and 4-acyloxy-2-aryl-6-oxo-1,3-thiazines, the decomposition paths of the dicarbonyl and hydroxycarbonyl forms were determined. It was concluded on the basis of the obtained data that 2-aryl-4,6-dioxo-1,3-thiazines exist in the gas phase predominantly in the hydroxycarbonyl form.For Communication 63, see 1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1409–1412, October, 1987.