Acylphosphonates enols derived from

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 ... 

Enol phosphates phosphonates were also obtained by the reaction of perfluoroalkanoyl chlorides with triethyl phosphite. In this case, it was not possible to isolate the putative intermediate perfluoroacylphosphonates. This result is in contrast with the facile formation of bis (trialkylsilyl) trifluoroacetylphosphonates (see previous section), and it indicates that acylphosphonates derived from carboxylic acids with strongly electron-withdrawing groups can be prepared using tris(trialkylsilyl) phosphites. Such silyl phosphites seem to be uniquely suitable for this purpose, by virtue of their high reactivity in the first step and their steric hindrance, which presumably retards the second step. 

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). 

The field of acylphosphonates (a-ketophosphonates) has been reviewed previously This chapter will deal mostly with the advances made since the publication of the previous review however, results from the older literature will be included for completeness. This chapter includes functional derivatives of both the phosphoryl and the carbonyl groups. With regard to the phosphoryl group, this refers to acylphosphonic acids esterified to various degrees, and also to acylphosphonoamidates and to acylphosphonic mono-and dihalides. With respect to the carbonyl group, this refers mainly to enolates, enamines, oximes and hydrazones in which the closeness of the phosphoryl function has yielded a wealth of recent results. These are discussed separately in Sections II and IV. 

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