Dialkylammonium tert-Butylmethylphosphinites: Stable Intermediates for the Synthesis of P-Stereogenic Ligands

The preparation of shelf-stable crystalline salts of tert-butylmethylphosphinous acid borane 1 is described. X-ray analysis of diisopropylammonium tert-butylmethylphosphinite borane 4 revealed the existence of a cyclic hydrogen-bond network in the solid state which accounts for the increased melting point and stability. Dialkylammonium phosphinite boranes are convenient precursors of the chiral tert-butylmethylphosphine fragment. Compound 4 can be directly employed in SN2@P reactions with different nucleophiles to yield valuable P-stereogenic intermediates and ligands.