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

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 BBr3 is
a facile method for the ortho-borylation of N,N-diaryl-amide derivatives. Subsequent
addition of Et3SiH 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.