Acylphosphonates fragmentation

Fragmentation chemistry with C-P bond cleavage has also been demonstrated in acylphosphonate oximes. a-Hydroxyiminobenzylphosphonates (a-keto-phosphonate oximes) are reported to be precursors to monomeric phosphate, and can thus serve as phosphorylating agents [2]. Monomethyl hydroxyimi-nobenzylphosphonate fragmentation is also consistent with a dissociative mechanism [87]. 

Breuer, E., Karaman, R., Goldblum, A., and Leader, H., Sulfonic acid-induced fragmentation of dialkyl acylphosphonates. Formation of alkyl carboxylates and alkyl sulfonates, 7. Chem. Soc.. Perkin Trans. 2, 2029, 1988. 

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) . ... 

Another interesting case of acylphosphonate formation from a geminal bisphosphonate is presented by the fragmentation of l,2-dihydroxyethane-l,l-bisphosphonic acid. This compound is stable in base, but fragments in acidic solution to phosphoric and acetylphos-phonic acids (equtation 38) ... 

When the preparation of alkali metal enolates derived from alkanoylphosphonates was attempted by treatment with strong anhydrous bases such as lithium diisopropylamide or sodium hydride, the formation of phosphate phosphonate-type products was observed. This was interpreted in terms of fragmentation of the enolate formed in the first step to ketene and dialkyl phosphite anion (equation 75), and addition of the latter to the carbonyl group of an unreacted acylphosphonate molecules to form a bisphosphonate. Such molecules are known to rearrange to phosphate phosphonates ... 

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