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

• Reaction of tridentate ligands with phenylboronic acid gave [4.3.0] and [4.5.0] heterobicyclic systems.
• Reaction conditions must be full controlled to obtain just one product.
• DFT calculations, PBE/6-31G(d,p), were performed in order to evaluate steric effects in the structures.
• Seven membered ring shows a chair conformation but the difference in energy with boat is minimal.
• Suzuki reaction can be achieved because a tricoordinated boron atom is found in some of the structures.

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, 8band9a 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.

Reaction of tridentate ligand 2-[(2-Hydroxy-ethylimino)-phenyl-methyl]-phenol 5b with one and two equivalents of phenyl and naphthyl boronic acid in toluene during 24 h and 1 h. give place to the synthesis of the monomeric boronates with fused five–six membered rings [4.3.0] and fused six–seven membered rings [4.5.0] respectively.Figure optionsDownload as PowerPoint slide