Kinnear–Perren reaction

In organophosphorus chemistry, the Kinnear–Perren reaction (sometimes the Clay-Kinnear-Perren reaction) is used to prepare alkylphosphonyl dichlorides (RP(O)Cl₂) and alkylphosphonate esters (RP(O)(OR')₂).^[1] The reactants are alkyl chloride, phosphorus trichloride, and aluminium trichloride as catalyst.^[2] The reaction proceeds via the alkyltrichlorophosphonium salt:

RCl + PCl₃ + AlCl₃ → [RPCl₃]⁺AlCl₄⁻

Reduction of this trichlorophosphonium intermediate with aluminium powder gives alkyldichlorophosphines (RPCl₂).

Partial hydrolysis of the same intermediate gives the alkylphosphonyl dichloride:

[RPCl₃]⁺AlCl₄⁻ + H₂O → RP(O)Cl₂ + AlCl₃ + 2 HCl

The reaction was first reported by Clay^[3] and expanded upon by Kinnear and Perren, who demonstrated that the four chlorinated methanes (CH_4−xCl_x) give the corresponding CH₃-, CH₂Cl-, CHCl₂-, and CCl₃-substituted derivatives. They also demonstrated workup with hydrogen sulfide to give the alkylthiophosphoryl dichlorides.^[4]