Direct Conversion of Phosphonates to Phosphine Oxides: An Improved Synthetic Route to Phosphines Including the First Synthesis of Methyl JohnPhos

Abstract

I.General Considerations Unless stated otherwise, reactions were conducted in oven-dried glassware under an atmosphere of nitrogen. Diethylether and tetrahydrofuran were dried using a DriSolv system using CuO and molecular sives under argon, all other reaction solvents were purified and dried according to literature. 1 All commercially obtained reagents were used as received unless otherwise specified. Organomagnesium reagents synthesized were titrated before use using either diphenylacetic acid 2 or no-d NMR 3 to determine molarity and stored under an atmosphere of argon gas at room temperature. Thin-layer chromatography (TLC) was visualized using low wavelength ultraviolet light (UV) for all aryl species or phosphomolybdic acid otherwise. Gas chromatography (GC) was performed on an Agilent Technologies 6850 Series II. 1 H NMR spectra were recorded on a Varian spectrometer (at 300.09 MHz or 500.02 MHz) and are reported relative to the residual solvent signals or the internal standard. Data for 1 H NMR spectra are reported as follows: chemical shift (δ ppm), multiplicity, coupling constant (Hz) and integration. 31 P{ 1 H} NMR spectra were recorded on a Varian spectrometer (at 121.48 MHz or 202.13 MHz) and are reported relative to an external standard of 0.1% H3PO4 in D2O at 0 ppm. Infrared spectra were taken using Nicolet Magna-550 Fourier Transform Infrared Spectrophotometer in ATR mode.

Synthesis, Structure and Nickel Carbonyl Complexes of Dialkylterphenyl Phosphines

“…All phosphines but L16 and L9 can be produced on gram‐scale runs in 50–60 % yields, hence comparable to those given originally for dialkylbiaryl analogues and for the recently prepared PMe 2 Ar′ (Methyl‐JohnPhos; ca. 52 % three‐step overall yield) . With the exception of PEt 2 Ar , L16 , reported to form in unexpected low yields (about 40 %), it can be noticed that sterically demanding R groups provoke a significant decrease in isolated yields, which remain in the 35–60 % range for i Pr, c ‐C 5 H 9 and c ‐C 6 H 11 , in contrast with the 70–80 % values of the PMe 2 Ar′ analogues.…”

The synthesis of heteroleptic phosphines

“…54,55 A recent development in our laboratory showed that direct and high-yielding P-C functionalization at phosphonates was possible without decomposition or the need for multistep chlorination. 56 In a typical reaction of a Grignard reagent with phosphonate, a pentavalent phosphorus intermediate quickly reacts with free halide in solution to form coordination salt oligomers (Scheme 10, top route). This reaction is mechanistically similar to the Michaelis-Arbuzov reaction and accounts for the complete consumption of phosphonate starting material and low yields of phosphine oxide.…”

Synthesis of Unsymmetrical Bis(phosphine) Oxides and Their Phosphines via Secondary Phosphine Oxide Precursors

“…The development of synthetic routes to tertiary phosphines via air-stable intermediates and easier workups has been of great interest to our research group [31,32]. In this work, we demonstrate the synthesis of unsymmetric bidentate phosphines utilizing air-stable phosphine oxide starting materials and intermediates.…”