Vinylphosphonic acid can be prepared by the reaction of PCl and acetaldehyde:
:PCl + CHCHO → CHCH(O)
This adduct reacts with acetic acid: 
: CHCH(O) + 2 CHCOH → CHCH(Cl)PO(OH) + 2 CHCOCl
This chloride undergoes dehydrochlorination to afford the target:
:CHCH(Cl)PO(OH) → CH=CHPO(OH) + HCl
In the Kinnear–Perren reaction alkylphosphonyl dichlorides and esters are generated by alkylation of phosphorus trichloride in the presence of aluminium trichloride.  Alkyltrichlorophosphonium salts are intermediates:
:PCl  +  RCl  +  AlCl  →  RPCl + AlCl
The RPCl product can then be decomposed with water to produce an alkylphosphonic dichloride RP(=O)Cl.