Cascade approach to synthesize BIMs and analogues in different nucleophilic conditions

Abstract

We report here a cascade synthetic approach to prepare 3,3′-bis(indolyl)methanes (BIMs) and analogues from single reactant 1H-indole-3-carbaldehydes under the reductive condition using NaBH₄. Uniformly, in another strategy, 1H-indole-3-carbaldehydes produced BIMs as a cascade product under Grignard reaction conditions. This is the first application of organometallic and reductive nucleophilic condition, where indole-3-carbaldehydes underwent NaBH₄ reduction/ methyl Grignard addition to form 1°/2° alcohol followed by elimination and subsequent addition of another molecule of indole aldehyde provided symmetric BIMs as unambiguous cascade products (22 analogues) in good to excellent yields.