Nitrosierung von 2-Aryl-3,5-dimethyl-1,1-dioxo-1,2-thiazinen - eine ungew�hnliche Ringtransformation zu mesoionischen Pyridaziniumsalzen

Abstract

Nitrosation of 2-Aryl-3,5-dimethyl-1,1-dioxo-1,2-thiazines – an Unusual Ringtransformation to Mesoionic Pyridazinium Salts The thiazines 1b–e, g, h react with isoamyl nitrite/HClg by nitrosation of the 3-methyl group to the 3-cyano-thiazines 3b–e, g, h. As by-products the mesoionic pyridazinium salts 4b, c are formed. The compounds 4b–i and 4–1e–i became main products by the nitrosation of 1b–i with sodium nitrite/HCl. In this case as by-products the oximes 2b–d were isolated, which can be transferred with sodium nitrite into 4b–d. The regioselectivity of the nitrosation reaction of 1 is influenced by the substituents of the aryl group.