Organophosphorus Intermediates. VI. The Acid-Catalysed Reaction of Trialkyl Orthoformates with Phosphinic Acid

Article abstract of DOI:10.1071/CH9800287

Trialkyl orthoformates react with phosphinic acid to give the corresponding alkyl phosphinate and alkyl mono- or bis-(dialkoxymethyl)phosphinates; dialkyl phosphonites and phosphine, PH3, are also formed.The formation of P-alkylated products is acid-catalysed and is believed to proceed by alkylation of the trivalent tautomer of phosphinic acid (or its ester) by the dialkoxymethyl carbonium ion arising from the ortho ester in the presence of acid.A comparison with the corresponding reactions of phosphonic acid suggests that the trivalent tautomer of phosphinic acid is formed much more readily than the trivalent form of phosphonic acid and this is accounted for by proposing that the equilibria RPH(O)OR' + H⁺ <*> RP⁺H(OH)OR' <*> RP(OH)OR' + H⁺ (R=H,OH; R'= H, alkyl) lie further to the right for R=H than for R=OH because of inductive effects. 31P and 1H n.m.r. data are reported