Triplet Energy and π‑Conjugation Effects on Photoisomerization of Chiral N,C-Chelate Organoborons with PAH Substituents

Chiral,
PAH substituted N,C-chelate boron compounds are systematically
investigated to establish the effect of triplet energy and substitution
position on their photoreactivity. They all undergo regioselective
photoisomerization, forming new dark isomers with quantum efficiencies
reflecting these various factors. New PAH fused 4bH-azaborepins are obtained via thermal isomerization of the dark isomers.
These results further implicate a photoactive triplet state in the
photoisomerization process and its utility in achieving rare PAH-fused
azaborepin-like heterocycles.