Radikalreaktionen von N‐Heterocyclen. I. Synthese und Struktur eines N,N‐verknüpften Bipyrazols

Abstract

Radical Reactions of N‐Heterocyclic Compounds. I. Synthesis and Structure of an N,N‐Linked Bipyrazole 5(3)‐Amino‐3(5)‐(phenylamino)‐pyrazole‐4‐carboxylic acid ethyl ester ( 1 ), which is a very good antioxidant, reacts under mild reaction conditions with dibenzoyl peroxide or with tert.‐butoxy radicals under formation of a bipyrazole 4 . Evidence of the structure of 4 is given by 1 H‐n.m.r., 13 C‐n.m.r., i.r. and u.v. spectroscopic measurements, respectively and especially by 15 N‐n.m.r. measurements of 15 N labelled compounds 1 and 4 . The bispyrazole 4 reacts with Pb(IV)‐acetate, the product isolated was the 5‐amino‐e‐anilino‐1‐(1‐anilino‐2‐cyano‐2‐ethoxycarbonylethenyl‐azo)‐pyrazole‐4‐carboxylic acid ethyl ester (7). The formation of this substance is a chemical proof of the structure of 4 .