Cyclization of β-hydroxyalkylphosphine oxides - Mechanism elucidation using experimental and DFT methods

Abstract

β-Hydroxyalkylphosphine oxides undergo an intramolecular electrophilic cyclization reaction in strongly acidic media. The main product in cases where rearrangement of the starting β-carbocation is possible possesses the benzophosphorinane skeleton. To gain insight into the mechanism of this transformation, both experimental methods and DFT calculations have been used. The data show a clear dependence of the selectivity of the reaction on both the amount and the concentration of the acid. NMR experiments provided some insight into the transformation of the substrate whereas DFT calculations explain the preferential formation of benzophosphorinane skeleton.