Thermal Cyclization of enaminoimine hydrochlorides of 2,5-dichloro-3,4-diformyl(N-substituted phenyl)pyrroles

A. P. Rajput and Deepak V. Nag

Abstract

Pyrroles possess wide spectrum of biological activities and are calcium & sodium channel blockers. Formyl group present on Pyrrole molecules make them promising precursors for further synthetic transformations. In view of this literature search and in continuation of our interest on the Vilsmeier-Haack Reaction and its synthetic utility[14]. We have synthesized 2,5-dichloro-3,4-diformyl(N-substituted phenyl)pyrroles. These compounds were obtained from N-substituted succinimides upon reaction with V-H reagent. The succinimides in turn were synthesized from succinic acid and substituted aryl amines. The dichloro diformyl compounds obtained after V-H reactions are having formyl groups & chlorine at suitable proximity hence may show promise as precursors for still other novel pyrrole derivatives, heterocyclic Schiff bases & other fused five, six and seven member cyclic rings. By keeping this view in mind we treated dichloroaldehydes with 4.4 equivalents of arylamines in ethanolic HCl at 0oC temp which formed the corresponding enaminoimine hydrochlorides in very good yields. These on thermal cyclization at 200-210 o C for 8-10 min in preheated oil bath formed symmetrical polycyclic compounds. These compounds are expected to show cytotoxic activities. All the resultant compounds are characterized by Spectral & elemental analysis.

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