Coordination-Controlled Nickel-Catalyzed Benzylic Allylation of Unactivated Electron-Deficient Heterocycles.

Abstract

Heterocycles are widespread in pharmaceuticals but methods for their transition metal-catalyzed functionalization remain limited. This report describes a general, mild, and effective nickel-catalyzed benzylic allylation and benzylation of 14 types of heterocyclic aromatic compounds, including pyridines, pyrazines, pyrimidines, pyridazines, triazines, benzimidazoles, oxazoles, thiazoles, as well as 3,3-dimethyl-indoles. The exquisite selectivity for benzylic sites at the 2-position is hypothesized to be controlled by coordination of a heterocyclic nitrogen to Zn(TMP)2 subverting generally presumed pKa 's of benzylic protons. Furthermore, the broad range of heterocyclic substrates, the diversity of electrophiles, and excellent functional group compatibility suggest its future application to synthesis of complex molecules and library diversification in drug discovery.