Synthesis and reactions of N-(azulen-1-ylmethylene)arylamines

Abstract

N-(Azulen-1-ylmethylene)arylamines, 5, were obtained in a fast quantitative conversion and high yield from the condensation of the corresponding azulene-1-carbaldehydes with aromatic amines without solvent. The reactions of the Schiff bases obtained, 5, were compared to those of the corresponding azo compounds 1a which have already been studied. The lack of regioselectivity in the oxidation of 5 with anhydrous FeCl₃ at both the azulenyl and at the aryl moiety, in contrast with the oxidation of compounds 1a which react mainly at the aryl, is in agreement with the differences of the calculated Fukui one electron reactivity index squared (I_R²) for the reactive positions in these molecules. From the calculated net charge for different positions in the molecules, a regioselective course for the electrophilic halogenation with CuCl₂ for both compounds 1a and 5 (at C3 in the azulene moiety) can be foreseen. However, the Schiff bases were chlorinated also at the aromatic ring; an explanation was proposed for this behaviour.