Synthesis of 6-Amino- and 6-Arylazoazulenes via Nucleophilic Aromatic Substitution and Their Reactivity and Properties

The nucleophilic aromatic substitution (S N Ar) reaction of diethyl 6-bromoazulene-1,3-dicarboxylate ( 1 ) with a variety of amines afforded the corresponding 6-aminoazulene derivatives 2a – 2j in good-to-excellent yields. 6-Aminoazulene derivatives 3a – 3f without the 1,3-diethoxycarbonyl functions were obtained by the deesterification of 2a – 2f with 100% H 3 PO 4 . The reactivity of 6-aminoazulenes toward the bromination, S N Ar, and palladium-catalyzed cross-coupling reactions was also clarified. 6-Arylazoazulenes 13a – 13c were also prepared via the S N Ar reaction of 1 with arylhydrazines, followed by oxidation with Pb(OAc) 4 in the presence of N 2 H 4 . The structural, optical, and electrochemical properties of the 6-amino- and 6-arylazoazulenes were revealed by single-crystal X-ray structure analysis, UV/vis spectroscopy, voltammetry analysis, spectroelectrochemistry, and theoretical calculations.