Cobalt-catalysed CH-alkylation of indoles with alcohols by borrowing hydrogen methodology

Abstract

A general heterogeneous cobalt-catalysed CH-alkylation of indoles with alcohols is reported. Utilizing this straightforward borrowing hydrogen methodology, a series of substituted and functionalized indoles were easily coupled with benzylic, heterocyclic, and aliphatic alcohols including methanol to prepare >65 substituted indoles in good to excellent yields. The resulting products represent an interesting class of heterocyclic compounds widely used in organic synthesis and medicinal chemistry. Key for this synthesis is the use of specific cobalt-nanoparticles supported on N-doped carbon, which were conveniently prepared by the pyrolysis of a templated material generated in situ by mixing cobalt-nitrate, zinc-nitrate, 2,6-diaminopyridine, and colloidal silica, and subsequent removal of silica.