A Direct One-Step Preparation of Triarylverdazylium Salts from the Corresponding Triarylformazans

Abstract
6-(4-Substituted-phenyl)-2,4-diphenylverdazylium salts 2 (8 examples, 55-93%) were prepared by the reaction of 3-(4-substituted-phenyl)-1,5-diphenylformazans 1 with formaldehyde and different organic and inorganic acids in a two-phase chloroform/water medium by brief and gentle heating. Self-phase-transfer catalysis is apparently involved. Subsequent reductions of the salts 2 with excess ascorbic acid in the two-phase system give the corresponding verdazyl radicals, while in methanol the reduction proceeds to form leuco-verdazyls.

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