Highly enantiomerically enriched chlorophosphine boranes: synthesis and applications as P-chirogenic electrophilic blocks.

The stereoselective synthesis of P-chirogenic chlorophosphine boranes 4 was investigated by HCl acidolysis of the corresponding aminophosphine boranes 10. The reaction afforded the P-N bond cleavage with inversion of the configuration at the phosphorus center, leading to the chlorophosphine boranes 4 with high to excellent enantiomeric purities (80-99% ee), except in the case of the chloro-1-naphthylphenylphosphine borane 4d. Reaction conditions and workup significantly influence the enantiomeric purity of the product, with the exception of the o-anisyl- and o-tolylchlorophenylphosphine boranes, 4b and 4c, which were found to be particularly stable even after purification by chromatography on silica gel.

Configurational stability of chlorophosphines.

The configurational stability of chlorophosphines is investigated. Several mechanisms involving chlorophosphine monomer, dimers, and adducts with HCl are evaluated by density functional theory calculations. The presence of HCl in the medium is found to catalyze the P-center chiral inversion at room temperature.