Kinnear–Perren reaction explained

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]

References

1. Encyclopedia: Svara, J. . Weferling, N. . Hofmann, T.. Phosphorus Compounds, Organic. Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. Weinheim. 2008. 10.1002/14356007.a19_545.pub2. 978-3-527-30673-2. .
2. The Synthesis of Dialkyl α-Halogenated Methylphosphonates. Rachel Waschbüsch . John Carran . Angela Marinetti . Philippe Savignac . Synthesis. 1997. 1997. 7. 727–743. 10.1055/s-1997-1417.
3. Clay. John P. . A New Method for the Preparation Of Alkane Phosphonyl Dichlorides . The Journal of Organic Chemistry . June 1951 . 16 . 6 . 892–894 . 10.1021/jo01146a010.
4. Formation of Organo-Phosphorus Compounds by the Reaction of Alkyl Chlorides with Phosphorus Trichloride in the Presence of Aluminium Chloride. A. M. Kinnear . E. A. Perren . J. Chem. Soc.. 1952. 3437–3445. 10.1039/JR9520003437.