Borylation–Reduction–Borylation for the Formation of 1,4-Azaborines

Abstract

Given the current interest in materials containing 1,4-azaborine units, the development of new routes to these structures is important. Carbonyl directed electrophilic borylation using BBr 3 is a facile method for the ortho -borylation of N , N -diaryl-amide derivatives. Subsequent addition of Et 3 SiH results in carbonyl reduction and then formation of 1,4-azaborines that can be protected in situ using a Grignard reagent. Overall, borylation–reduction–borylation is a one-pot methodology to access 1,4-azaborines from simple precursors.

Boron-containing helicenes as new generation of chiral materials: opportunities and challenges of leaving the flatland

“…The Ingleson group, with extensive expertise in the electrophilic borylation of various heterocycles, 78–81 and our group reported the synthesis, resolution and characterization of the (chir)optical properties of the first configurationally stable core-non-extended [5]- and [6]helicenes 65–67 embedding an azaborine ring, where the B–N bond is located on the outer helicene rim. 82 The attempts to prepare 65 using BCl 3 /AlCl 3 under forcing conditions (up to 175 °C) or BBr 3 at 75–150 °C either failed or the conversion was relatively low (<30%).…”