Alkylphosphonate esters

The reaction proceeds through an intermediate phosphonium salt which can be isolated in some instances. The Michaehs-Arbusov reaction is especially useful for converting trialkyl phosphites, (RO) P, to alkylphosphonic esters, and to esters of phosphonocarboxyhc acids. 

Olefination Reactions Involving Phosphonate Anions. An important complement to the Wittig reaction involves the reaction of phosphonate carbanions with carbonyl compounds 253 The alkylphosphonic acid esters are made by the reaction of an alkyl halide, preferably primary, with a phosphite ester. Phosphonate carbanions are generated by treating alkylphosphonate esters with a base such as sodium hydride, n-butyllithium, or sodium ethoxide. Alumina coated with KF or KOH has also found use as the base.254... 

Kawase, T., Yoneda, S., and Yoshida, Z.-i., Synthesis of alkylphosphonic esters by the reactions of aliphatic thiones with trialkyl phosphites, Bull. Chem. Soc. Jpn., 52, 3342, 1979. 

Alkylphosphonate esters. Phosphonate esters with P-alkyl groups of different chain lengths can be prepared from iodoalkylphosphonates (alkyl being methyl, ethyl, propyl) and 1 -alkenes by a radical addition process, using an initiating system comprising BujSnCl, NaBH, and EtjB (Oj). 

Hydrazoic acid can also be used to convert (alkoxycarbonyl)alkylphosphonic esters into aminoalkylphosphonic acids (Schmidt rearrangement. Scheme 8.93). °... 

Since alkylphosphonate esters of nucleosides are generally more stable to nucleases and have greater cell permeability, 5 -deoxyphosphonate nucleotide analogues with 1,2-oxaphosphinane structures have been synthesized <95JOC2563>. 

Alkylphosphonate esters. The carbanion generated from dechlorination with BuLi condenses with aldehydes (and some ketones). Catalytic hydrogenation of the (chlorovinyl)phosphonate products affords phosphonates. 

Z = Pr 0 or Et2N = Et2N or (CH2)n, n = 4-6) the latter exist as mixtures of keto and enol tautomers, the latter as ( ) plus (Z) mixtures. Also, carbanions from non-functionalized alkylphosphonic esters react with the reagent (178) to give (179) which may be hydrolysed to the (2,3-dioxoalkyl)phos-phonates (180). ... 

Both mono and dichlorides can be obtained by treating phosphorus trichloride with dialkyl-phosphinous and alkylphosphonous esters, respectively (6.145, 6.146), or with primary phosphinic acids (6.213). The addition of terminal alkenes to PCI3 under free radical conditions produces P-chloroalkylphosphonous dichlorides (6.147). 

Transesterification of a Phosphonate with a Diol. This method proceeds well in the case of 0,0-dialkyl hydrogen phosphonates (101) but less selectively with 0,0-dialkyl alkyl- or arylphosphonates. With 0,0-diaryl alkylphosphonates, ester exchange is an effective route to pol5uneric phosphonates (102-104) ... 

The synthetic utility of lithium salts of (l-methylthio)alkylphosphonate esters for the preparation of ketones is reported in an extension of the Wadsworth-Emmons-Horner modification of the Wittig reaction. ... 

For the scope and development of this synthesis of vinyl sulfides with lithio (l-methylthio)alkylphosphonate esters (i) via the Emmons-Horner phosphonate reaction, see E. J. Corey and J. I. Shulman, J. Org. Chem., 35, 777 (1970). This synthesis utilizes the ability of electron-withdrawing substituents, such as a thioalkyl moiety, on the carbon a to the phosphorus function to promote Wittig elimination (i- ii) of -hydroxy phosphonates which are generally unreactive. The resulting vinyl sulfides readily undergo mercury(ll)-promoted hydrolysis to ketones. 

---