Direct access to pyrrole anhydrides via oxidative self-coupling of pyrrole carboxaldehydes
Surabhi Panday1, Tapas Maity1, Pratibha Bhatti1
1Department of Pharmaceutical Technology (Process Chemistry), National Institute of Pharmaceutical Education and Research (NIPER) S.A.S. Nagar, Punjab 160062, India. jlaha@niper.ac.in.
Abstract:
An elegant synthesis of pyrrole-2-carboxylic acid anhydrides from pyrrole-2-carboxaldehydes using TBAI as a catalyst and tert-butyl hydroperoxide (TBHP) as an oxidant is described herein. Unlike the previous reports wherein pyrrole-2-carboxylic acids were invariably used, we report here for first time the oxidative self-coupling of N-benzyl pyrrole-2-carboxaldehydes for the synthesis of 1-benzyl-1H-pyrrole-2-carboxylic anhydrides. In addition, a one-pot synthesis of novel pyrrole-2-carboxamides from pyrrole-2-carboxaldehydes is also reported. The mechanistic investigation supports a previously unexplored oxidative self-coupling of a pyrrole acyl radical, leading to the synthesis of a carboxylic anhydride.
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