Phosphoryl carbanions

Diethyl (difluorolithiomethyl)phosphonate is proving valuable for the preparation of homologous (1, l-difluoroalkyl)phosphonic derivatives, either by direct alkylation or by acylation, using PhOC(S)Cl, of the product from the interaction of the phosphorylated carbanion and an aldehyde, and the subsequent treatment of the resultant diethyl [(1,1-difluoro-2-phenoxythiocarbonyloxy)alkyl]phosphonate with Bu3SnH (Scheme 9). ... 

The successful preparation of (2-hydroxyalkyl)phosphonic acid derivatives by the treatment of an appropriately phosphorylated carbanion with an aldehyde or ketone, has been further extended to the formation of 294 from 293". ... 

The simplest application of the Darzens reaction is outlined in Scheme 29. The production of the phosphoryl carbanion has been normally carried out with a metal alkoxide in this respect, r r -butoxide is better than ethoxide, some reactions proceeding only with the former base butyllithium or Ida has also been employed. The carbanion 357 is also available through the chlorination of dialkyl methylphosphonate carbanion with PhSO.CP ... 

Variations in the Darzens procedure include the generation, from one phosphorylated carbanion, e.g. 359, of a second carbanion, 360 (similar to 358 already encountered in Scheme 30), as a prelude to the Darzens displacement to give 361W en treated with tetrabutylammonium cyanide, the ester 362 yields both the epoxide 363 and the cyanooxo ester 364". ... 

The reactions of phosphorylated carbanions have been extended to include those with sulphinate esters as a route to phosphoryl sulphoxides . The interaction of dimethyl... 

ETHYNE via generation and trapping of an unstable phosphorylated carbanion is illustrated. The methodology is well suited tor the synthesis of a wide variety of terminal acetylenic compounds. 

The importance of the cation-oxygen interaction has also been pointed out in highly Z-selective olefination reactions of the a-silyl-a-phosphoryl carbanion 19 (Scheme 2.16) [41, 42]. The chelating Li-O interactions are likely to determine the configuration of the carbanion 19 in the approach of the aldehyde. This transition state leads to the formation of the kinetically favored adducts 20, which give the (Z)-alkenes 21 after syn-elimination of the oxophilic silylated moiety and hydrolysis. 

Scheme 2.16. Z-Selective Peterson reaction of an a-silyl-a-phosphoryl carbanion with aldehydes.

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