Verfahren zur Herstellung von Chinoxalin-N,N'-dioxyden

摘要

1,140,298. Quinoxaline- and fused quinoxaline dioxides. CHAS. PFIZER & CO. Inc. 31 May, 1967 [3 April, 1967], No. 25211/67. Heading C2C. Quinoxaline- and fused quinoxaline-N.N1- dioxides are prepared by a cumulative, continuous flow procedure comprising (1) reacting under monohalogenation conditions a ketone of the formula wherein R 1 is H or C 1 -C 5 alkyl, R 2 is C 1 -C 6 alkyl, phenyl, benzyl or beta-phenethyl or R 1 and R 2 taken together are C 3 -C 6 polymethylene, with substantially a molar equivalent of chlorine or bromine in an inert organic solvent; (2) reducing the hydrogen halide content of the reaction mixture to an amount such that a molar equivalent of o-phenylene diamine is soluble therein; (3) introducing the o-phenylene-diamine under an inert atmosphere under condensing conditions, and (4) adding a peroxycarboxylic acid or aqueous hydrogen peroxide, the temperature of the reaction mixture being maintained throughout below 50‹ C., until formation of the quinoxaline- N,N1-dioxide is substantially complete. In one of the examples, the formation of 1,2,3,4- tetrahydro - phenazine - N,N1 - dioxide is described. In order to reduce the amount of oxidizing agent used, oxygen may, in some circumstances, be passed through the mixture after condensation is complete.