Azofarbstoffe durch oxydative Kupplung, XVII. Farbstoffe aus Hydrazonen aromatischer 5‐Ring‐Heterocyclen mit 2 bis 4 Heteroatomen

Abstract

Es wird die oxydative Kupplung der Hydrazone I–VII1), die sich vom Pyrazol, Imidazol, 1.2.4‐Triazol, Tetrazol sowie vom 1.2.4‐ und 1.3.4‐Thiodiazol ableiten, mit 1‐Hydroxy‐naphthoesäure‐(2)‐anilid und 4‐Acetamino‐diphenylamin beschrieben. Die Spektren der entstehenden Farbstoffe werden diskutiert.

Synthesis of Azoimidazolium Dyes with Nitrous Oxide

“…[14] A method without diazonium salts was developed by Hünig et al: under oxidative conditions, hydrazones can be coupled to arenes (Scheme 1 C). [15,16] However, this procedure is limited to highly activated aromatic compounds such as anilines. In the following, we describe a novel procedure which is based on N-heterocyclic carbenes, N 2 O, arenes, and AlCl 3 (Scheme 1 D).…”

“…Published procedures include the coupling of imidazole with diazonium salts, followed by alkylation (A), [13] the direct coupling of N-heterocyclic carbenes with diazonium salts (B), [14] and the oxidative coupling of hydrazones with activated arenes. [15,16] The new procedure is based on N-heterocyclic carbenes, N 2 O, arenes, and AlCl 3 (C).…”

Synthesis of Azoimidazolium Dyes with Nitrous Oxide

“…A method without diazonium salts was developed by Hünig et al. : under oxidative conditions, hydrazones can be coupled to arenes (Scheme ) 15. 16 However, this procedure is limited to highly activated aromatic compounds such as anilines.…”

“… Retrosynthetic analysis of azoimidazolium dyes. Published procedures include the coupling of imidazole with diazonium salts, followed by alkylation (A),13 the direct coupling of N‐heterocyclic carbenes with diazonium salts (B),14 and the oxidative coupling of hydrazones with activated arenes 15. 16 The new procedure is based on N‐heterocyclic carbenes, N 2 O, arenes, and AlCl 3 (C).…”