Synthesis, characterization, X-ray studies and DFT calculations of fused five–six and seven–six membered ring of new heterobicyclic system of boron compounds

Two tridentate ligands derivated from ethanolamines and 2-hydroxyacetophenone and 2-hydroxybenzophenone were reacted with phenylboronic acid and naphthylboronic acid in different proportions to obtain compounds 7a, 8b and 9a which are [4.3.0] and [4.5.0] heterobicyclic systems. Compounds 7a, 8b and 9a were fully characterized and the structures of 7a and 8b have been analyzed by X-ray diffraction, where a series of parameters such as bond distances, bond angles, torsion angles, tetrahedral character at the boron atom, steric effects and deviation of the boron atom from the mean plane have been evaluated and comparated. DFT calculations, PBE/6-31G(d,p), were performed in order to evaluate steric effects and the stability of [4.3.0] and [4.5.0] heterobicyclic system.