Synthesis of monophosphines directly from white phosphorus

Abstract

Monophosphorus compounds are of enormous industrial importance due to the crucial roles they play in applications including pharmaceuticals, photoinitiators, and ligands for catalysis, among many others. White phosphorus (P4) is the key starting material for the preparation of all such chemicals. However, current production depends upon indirect and inefficient, multistep procedures. Here, we report a simple, effective 'one pot' synthesis of a wide range of organic and inorganic monophosphorus species directly from P4. Reduction of P4 using tri-nbutyltin hydride and subsequent treatment with various electrophiles affords compounds that are of key importance for the chemical industry, and requires only mild conditions and inexpensive, easily handled reagents. Crucially, we also demonstrate facile and efficient recycling and ultimately even catalytic use of the tributyltin reagent, thereby avoiding the formation of significant Sn-containing waste. Accessible, industrially relevant products include the fumigant PH3, the reducing agent hypophosphorous acid, and the flame-retardant precursor tetrakis(hydroxymethyl)phosphonium chloride. Main TextWhite phosphorus (P4) is one of the most important synthetic feedstocks for the modern chemical industry, 1 and is produced on a scale of > 1 Mt per year. The pyrophoric nature of P4 and its hazardous and energy-intensive synthesis from phosphate ores have prompted recent academic efforts to bypass this compound and instead use phosphate materials directly as synthetic precursors. [2][3][4] Other researchers have emphasized the need to develop more sustainable routes for the recycling and reuse of P-containing materials, which are otherwise 2 lost as environmentally-hazardous wastes. 2,5,6 However, despite these efforts, P4 remains the only industrially-viable precursor from which to prepare the vast majority of monophosphorus compounds, which find applications ranging from pharmaceuticals to chemical catalysts. [7][8][9] Unfortunately, state-of-the-art industrial methods for the synthesis of these useful P1 species rely on indirect and correspondingly inefficient multi-step processes. The most common route (Fig. 1a) involves oxidation of P4 by toxic Cl2 gas to generate extremely corrosive PCl3. 10 Treatment with suitable nucleophiles then provides the desired products via substitution of chloride, with concomitant generation of chloride-containing waste. Alternatively, some P1 products can be generated by hydrophosphination of unsaturated organic compounds using PH3 gas. However, industrial-scale preparation of PH3 involves acid-catalysed or alkalimediated disproportionation of P4, which demands harsh reactions conditions and produces phosphorus oxyacid derivatives as stoichiometric byproducts (Figure 1). 10 Recognition of the deficiencies of current routes for generating P1 products has prompted a strong desire to discover reactions that are capable of transforming P4 into these useful compounds directly, bypassing the need for isolation and manipulation of potentially hazard...

Pentaphosphaferrocene-mediated synthesis of asymmetric organo-phosphines starting from white phosphorus

“…The first one of these protocols involves the generation of aryl radicals from aryl halides induced by an unsaturated Ti(III) complex 22 . The fundamental synthetic approach of all these protocols involves either an electrochemical approach 23 or, more often, the generation of organo radicals from the corresponding halides induced by transition metal complexes 22,[24][25][26] as well as, quite recently, organotin-compounds 27 . These radical-promoted routes can be divided into stochiometric 22,24,27 and/or (photo)catalytic approaches 25,26 .…”

Generation of a π‐Bonded Isomer of [P4]4−by Aluminyl Reduction of White Phosphorus and its Ammonolysis to PH3

“…A very recent report demonstrated PH 3 synthesis via the photolytic activation of P 4 by Bu 3 SnH and subsequent protonolysis with excess HCl. [23] Using PPh 3 as an internal standard, we found the amount of PH 3 generated corresponded to a 23 % NMR yield (per P…”

Phosphafluorenyl lithiums: direct synthesis from white phosphorus, structure and diversified synthons

“…In 1963, the first example of direct P−C bond formation from P 4 to organophosphorus compounds was reported [35,36]. However, limited by the type of nucleophilic reagents and low selectivity of P−P bond cleavage, the functionalization of P 4 through direct P−C bond formation still has few examples [37][38][39][40][41][42][43][44][45][46]. Our group [47][48][49][50][51][52][53] has focused on P 4 functionalization since 2016, especially in the P−C bond formation.…”