o‐Hydroxyarylphosphanes: Strategies for Syntheses of Configurationally Stable, Electronically and Sterically Tunable Ambiphiles with Multiple Applications

Abstract

o‐Hydroxyarylphosphanes are fascinating compounds by their multiple‐reactivity features, attributed to the ambident hard and soft Lewis‐ and also Brønstedt acid‐base properties, wide tuning opportunities via backbone substituents with ±mesomeric and inductive, at P and in o‐position to P and O also steric effects, and in addition, the configurational stability at three‐valent phosphorus. Air sensitivity may be overcome by reversible protection with BH3, but the easy oxidation to P(V)‐compounds may also be used. Since the first reports on the title compounds ca. 50 years ago the multiple reactivity has led to versatile applications. This includes various P‐E‐O and P=C‐O heterocycles, a multitude of O‐substituted derivatives including acyl derivatives for traceless Staudinger couplings of biomolecules with labels or functional substituents, phosphane‐phosphite ligands, which like the o‐phosphanylphenols itself form a range of transition metal complexes and catalysts. Also main group metal complexes and (bi)arylphosphonium‐organocatalysts are derived. Within this review the various strategies for the access of the starting materials are illuminated, including few hints to selected applications.

Synthesis, characterization and stability of phosphonium phenolate zwitterions derived from a (diphenylphosphino)phenol derivative and oxiranes

“…3 Here we would like to report our contribution to a better understanding of the reaction of epoxides with phosphines. We have chosen a (diphenylphosphino)phenol derivative combining the phenol and the phosphine into a single molecule [20] to study in particular the first step of the reaction and found evidence for the elusive formation of phosphonium phenolate species reminiscent of II. The resulting zwitterionic molecules do not undergo the deoxygenation reaction and are thermally quite stable, making them potentially interesting as catalysts for various reactions such as the synthesis of cyclic carbonates from epoxides and CO 2 [21,22] or organophotoredox catalysis [23,24].…”