Closed-loop hydrostannylation of white phosphorus using Bu3SnCl and NaBH4: one-pot access to organophosphorus compounds

Abstract

The direct functionalization of white phosphorus (P₄) is gaining attention as an alternative to state-of-the-art multi-step processes. The hydrostannylation of P₄ affords valuable monophosphorus compounds directly via a hydrostannylphosphine mixture (Bu₃Sn)_xPH_3-x (where x = 0-3) that reacts with suitable electrophiles. However, previous reports required terminal reductants which are infeasible for industrial-scale applications. Here, we report an improvement in this chemistry using NaBH₄ as the terminal reducing agent, generating the key hydrostannylation agent Bu₃SnH in situ from Bu₃SnCl. The resulting (Bu₃Sn)_xPH_3-x mixtures were successfully functionalized towards useful P1 compounds. Furthermore, we present the 'one-pot' preparation of tetrakis(hydroxymethyl)phosphonium chloride (THPC), the subsequent direct recycling of Bu₃SnCl, and preliminary attempts towards the catalytic synthesis of THPC.