Acylphosphonates with carbanions

Side-reactions of a different type may result from zwitterionic carbanionic intermediates formed by the interaction of the freshly formed acylphosphonates with excess trialkyl phosphite (equation 17). Such ionic intermediates may undergo variety of reactions, depending on the nature and the R group, temperature and whether other reactive molecules are present in the reaction mixture. The zwitterionic intermediate may react with electrophiles or lose phosphate to from novel carbene intermediates as shown in the following sections. 

Carbanions derived from isocyanoacetates formed in situ using NaH react with acylphosphonates to give l-alkyl-2-ethoxycarbonyl-2-formylaminoeth-l-enylphosphonates [45]. Cu20 catalysis provided stereoselectivity, giving mainly the Z-isomer. 

The course of the reaction between acylphosphonates and 1-nitroalkane carbanions depends on the nature of the acyl group. Thus, nucleophilic addition of nitromethane to acetylphosphonates in the presence of di- or triethylamine results in the formation of dialkyl 1-hydroxy-l-methyl-2-nitro-ethylphosphonates (R = Me, = H, Scheme 7.75)." " However, the procedure is not applicable to the synthesis of dialkyl 1 -hydroxy-l-pheny 1-2-nitrocthyIphosphonate because the electron-with-drawing ability of the benzene ring destabilizes the molecule toward alkali and results in C-P or C-C bond cleavage. The fact that diisopropyl 1-hydroxy-l-phenyl-2-nitroethylphosphonate was... 

The course of the condensation between an acylphosphonate and a 1-nitroalkane car-banion depends on the nature of the acyl group. Base catalysts are commonly employed, but an acylphosphonate derived from an aromatic acid requires an acidic catalyst otherwise the intermediate anion fragments to hydrogenphosphonate and nitroketone (Scheme 20)207 jYiQ reaction between a nitroalkane carbanion and a dialkyl (trichloroacetyl)phos-phonate results in a rearrangement to phosphate with additional dehydrochlorination (Scheme 21) . ... 

Among monoesters that are generally stable at pH 7.4, the crotonoyl derivative is exceptional in its instability at this pH. It was proposed that the decomposition of this compound may be initiated by a Michael-type addition of hydroxide ion to the double bond, to form an enolate anion, which would decompose by analogy with what was observed for a-carbanions derived from acylphosphonates (equation 52). 

Further work showed that stabilized ylides can also react with acylphosphonates. Ethoxycarbonyltriphenylphosphorane and triethyl phosphonoacetate carbanion (Horner-Emmons reagent) give trisubstituted vinylphosphonates of the opposite stereochemistry as main products (equation 64)... 

It was recognized that an acylphosphonate or acylphosphinate might act as an effective inhibitor against plant PDHc. Both compounds could compete with pymvate for the active site of plant PDHc El by binding with TPP resulting a TPP complex. It was speculate that, a highly reactive carbanion of TPP should nucleophiUcaUy attack carbonyl carbon atoms of 1-2 to readily form a phosphinic adduct which resembled normal reactive intermediate a-lactyl-TPP. Once it was bond, the normal decarboxylation process in plant was shut off and plant die as their... 

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