Anionic Phosphorus as a Nucleophile. An Anion Chain Arbuzov Mechanism

Article abstract of DOI:10.1021/jo00377a009

The reaction of the anion of dineopentyl phosphonate with alkyl iodides is kinetically second order and yields the P-alkylated dineopentyl alkylphosphonate.This supports, as previously suggested, a simple S_N2 mechanism for the reaction.Rate constants in sulfolane are reported.Trimethyl phosphate and phosphonate esters also alkylate this nucleophile. hen dimethyl phosphonate dissolved in tetrahydrofuran or in benzene is treated with solid sodium hydride at room temperature, the initially formed anion is virtually quantitatively alkylated by remaining neutral ester before it can react with sodium hydride, yielding monomethyl phosphonate anion and dimethyl methylphosphonate.This major side reaction is less important with diethyl phosphonate and is not detected with the neopentyl ester.It does not occur with butyllithium as the base or with sodium hydride at -78 deg C in either THF or benzene as the solvent.This fast reaction appears to be a surface reaction.The anion of diphenylphosphinite is similarly alkylated my methyl diphenylphosphinite, yielding methyldiphenylphosphine oxide and regenerating the anion, thus constituting a new anionic chain mechanism for the Arbuzov reaction.