Phosphoryl anion

Hosseini, M. W., Supramolecular catalysis of phosphoryl anion transfer processes , in Supramolecular Chemistry of Anions, Bianchi, A., Bowman-James, K., Garcia-Espana, E., eds. Wiley New York, 1997 pp 421-448. 

Mechanistic studies have been reported on the addition of alkylphosphonic acid reagents (325) to trialkyl-substituted epoxides (326). The addition occurs according to a three-step mechanism starting with rapid nucleophilic attack of the phosphorylated anion on the most alkyl-substituted carbon of oxirane, followed by formation of a dioxaphospholane structure (327) with release of... 

The regioselectivity of the addition of phosphorylated anions to a/5-unsaturated ketones has been studied in some detail, - and has been discussed in terms of perturbation theory. Most products arise from nucleophilic attack at the C==C bond. The condensation of phosphonates with aromatic aldehydes may be carried out in a two-phase system in the absence of a typical phase-transfer catalyst. Among those aldehydes and ketones used successfully in alkene syntheses with phosphonates are (97), (98), (99), and (100). ... 

Sn2 Nucleophilicity of (CH30)2P0. To determine the intrinsic SN2 kinetic nucleophilicity of (CH30)2P0, we investigated the reactions of the anion with the series of CH3X molecules listed in Table V. The rates of these reactions vary from modest with the most reactive CH3I molecules to slow with CH3Br to no observed reaction with CH3C1. From the results, we conclude that the phosphoryl anion is kinetically a poor nucleophile in SN2 displacement reactions. 

The phosphoryl anion is an ambident species and the calculated AHf values (19) of the tautomers (CH30)2P(=0)CH3 ( — 210.2 kcal/mol) and (CH30)3P ( — 167.6 kcal/mol) differ by 43 kcal/mol. Whether methyl transfer occurs to phosphorus of the anion (thermodynamic control) where a large intrinsic barrier exists or at oxygen under kinetic control with a smaller intrinsic barrier is not clear at this time a much lower reaction exothermicity exists in this latter mode. 

Reactions Involving Electron Transfer. To model the first step in the SRN1 mechanism of electron transfer from the anion to the neutral substrate, we examined the reactions of the phosphoryl anion with the XCF3 molecules where X = I, Br, or Cl ... 

The ambident phosphoryl anion (MeO)2PO is a weak nucleophile in the gas phase further, the neutral products in its reactions with MeX (X = Cl, Br and I) remain uncertain. Methyl transfer to PO would result in (Me0)2P(0)Me while methyl transfer to O would result in (MeO)3P. 

Homer-Wadsworth-Emmons reaction remained unimportant as a preparative route owing to the low reactivity of (136) (Pommer, 1960) toward phosphoryl anions. 

The carboxylic acids (332) and (333) are retinoids lacking a terminal ring system. The carbon skeletons of the two compounds were built in accordance with the (Ci8 + C2) method via Reformatsky reactions (Augustyn et al., 1971). The aldehyde (334) was synthesized using a PO-stabilized phosphoryl anion in conventional reaction steps (Crouch, 1982). 

Many enzymes that mediate phosphoryl transfer from ATP are thought to do so via the formation of a phosphorylated imidazole residue of histidine (Scheme 49). Spontaneous reactions of amines with ATP are legendarily slow, but now a systematic study, involving trapping of the phosphorylated amine with F , has shown that amines (pyridines, imidazoles) react with ATP 30-100-fold faster than do water or alcohols. To complicate the interpretation of the results, it was found that the rate constant for the reaction of F with ATP tetraanion is similar to rate constants for reaction of uncharged amine and oxygen nucleophiles, thus dispelling the myth that reactions of ATP and other phosphoryl anions with anionic nucleophiles are prevented by electrostatic repulsion in aqueous solution. ... 

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