Synthesis and Reactivity of Tris(Hydroxymethyl)Phosphine-Mimicking Nonsymmetrical Diphosphine Ligands

GRAPHICAL ABSTRACT

Abstract

As part of a study to obtain well-defined tris(hydroxymethyl)phosphine (THP)-inspired ligands, a new nonsymmetrical diphosphine featuring two hydroxymethyl functional groups on one phosphine terminus has been synthesized. A double formylation reaction was employed to effect the hydroxymethylation of the primary phosphine function in Ph₂P(CH₂)₂PH₂ and furnish the target bis(hydroxymethyl)phosphanylethyldiphenylphosphine. Initially, this methodology afforded complex product mixtures whose composition varied according to the reaction solvent, and these are assumed to result from acetalization of excess formaldehyde by the hydroxymethyl groups of the anticipated phosphine. The desired target could be obtained via a borane protection – deprotection pathway or by repeatedly treating the product mixture with H₂O, thereby probably shifting a hemiacetal equilibrium of the phosphine with formaldehyde towards the free hydroxymethyl functionalities.

Keywords::

• Tris(hydroxymethyl)phosphine
• phosphine borane deprotection
• phosphine formylation