Vilsmeier–Haack reaction with succinamidals. A convenient synthesis of 5-chloropyrrole-2-carboxaldehydes and 5-chloropyrrole-2,4-dicarboxaldehydes

Abstract

It is shown that the reaction of N-alkylsuccinamidals (2) with the Vilsmeier–Haack reagent derived from DMF and phosphorus oxychloride can be controlled to preferentially produce either 5-chloropyrrole-2-carboxaldehydes (8) or 5-chloropyrrole-2,4-dicarboxaldehydes (9). The corresponding N-unsubstituted aldehydes are obtained when N-tert-butoxycarbonylsuccinamidal (11) is the substrate in the above reactions. Keywords: Vilsmeier–Haack reaction, succinamidals, 5-chloropyrrole-2-carboxaldehydes, 5-chloropyrrole-2,4-dicarboxaldehydes.