Formation and Structural Characterization of Benzoxa- and Thienoxaphosphaborinines

Area of Science:

• * Organoboron Chemistry
• * Heterocyclic Chemistry
• * Supramolecular Chemistry

Background:

• * Exploration of novel heterocyclic systems is crucial for advancing chemical synthesis and materials science.
• * Boron-phosphorus heterocycles represent an underexplored class of compounds with potential for unique reactivity.
• * Understanding reaction mechanisms is key to controlling and optimizing synthetic pathways.

Purpose of the Study:

• * To report the synthesis of a new class of six-membered boron-phosphorus heterocycles: benzoxa- and thienoxaphosphaborinines.
• * To investigate the reactivity of these novel heterocycles with carbonyl compounds.
• * To elucidate the reaction mechanism using computational methods and structural analysis.

Main Methods:

• * Synthesis via aromatic lithiation of dioxazaborocans, followed by reaction with PhPCl2 and hydrolysis.
• * Condensation reactions with various aldehydes and ketones.
• * Density Functional Theory (DFT) calculations to study reaction mechanisms.
• * X-ray crystallography for molecular structure determination.

Main Results:

• * Successful synthesis of benzoxa- and thienoxaphosphaborinines.
• * Demonstrated facile condensation reactions with aldehydes and ketones.
• * DFT calculations indicated hydrogen bonding with the B(OH)2 group, not Lewis acid-boron interaction, as the primary activation mode.
• * X-ray crystallography revealed intermolecular BOH···O═P hydrogen bonding in the solid state.

Conclusions:

• * Benzoxa- and thienoxaphosphaborinines represent a novel and synthetically accessible class of heterocycles.
• * The condensation reactions proceed via a unique mechanism involving B(OH)2 hydrogen bonding, suggesting potential FLP-like behavior.
• * Intermolecular hydrogen bonding plays a significant role in the self-assembly of these molecules in the solid state.