My inclination is to call this reaction a "phosphono-Claisen condensation." A  Claisen condensation is the alpha-acylation of an ester with another ester. In this case, the typical carbon-centered ester is replaced with a phosphonate, so phosphono-Claisen condensation specifies that difference.  Avoiding the proper name, "alpha-acylation of a phosphonate" is a suitable description of the reaction.

Montchamp and coworkers published a paper describing the "phospha-Claisen" reaction, which they limit to the condensation of two phosphonates to give a 1,1-diphosphono compound. 

The [website][1] maintained by the venerable Hans Reich describes this reaction as "Claisen-like":
 

> (MeO)2P(O)CH2Li will also react with carboxylic acid derivatives like
> esters, lactones and amides in a Claisen-like reaction to form keto
> phosphonates.

The [Organic Chemistry Portal][2] describes the reaction as "the condensation of esters and phosphonates."

A brief survey of the literature featuring this reaction type (Thanks SciFinder!) doesn't show any convention for naming this reaction beyond calling it the acylation of a phosphonate. In my SciFinder searching, the earliest usage of this reaction is from [1970][3], and that paper cites a [Corey paper from 1966][4]. That paper doesn't have a proper experimental on the reaction, but contains the note:

> Anions derived from 1 (X = H or alkyl) are of value in the synthesis
> of keto phosphonates 1 (X = RCO) by reaction with esters. The
> preparation of these intermediates, which are of value in olefin
> synthesis [see [H. Takahashi, K. Fujiwara, and M. Ohta, Bull. Chem.
> Soc. Japan, 35, 1498 (1962)\]][5], is usually impractical by the
> Michaelis-Arbusov reaction.

It's a little nebulous who performed this chemistry first, but perhaps someone could have christened it the "Corey-Claisen condensation" or the "Corey variant of the Claisen condensation". Of course there is already a Corey-Claisen *rearrangement* so this would be really confusing.


  [1]: http://www.chem.wisc.edu/areas/reich/chem547/1-carbonyl%7B19%7D.htm
  [2]: http://www.organic-chemistry.org/abstracts/lit2/676.shtm
  [3]: http://pubs.acs.org/doi/abs/10.1021/ja00713a034
  [4]: http://pubs.acs.org/doi/abs/10.1021/ja00975a057
  [5]: http://www.journal.csj.jp/doi/fpi/10.1246/bcsj.35.1498