Esters, phosphonic, with Grignard reagents

Equation (10) exemplifies a Hoerner olefination of phosphonic acid esters, using a Grignard reagent or magnesium alkoxide [Mg(OEt)2, not shown] as the base [13]. Magnesium bases gave superior yields with aliphatic aldehydes, compared with sodium and lithium bases. 

A major use for phosphoryl chloride is in the synthesis of phosphoryl esters (Chapter 6). It will also react with Grignard reagents to give phosphine oxides (6.112), and with secondary amines to give amino-substituted phosphine oxides or phosphonic dichlorides (7.96). 

Phosphonous diesters are reduced by lithium aluminium hydride to primary phosphines (6.58). With chlorine, chlorophosphonate esters are formed. Alkyl halides undergo the Arbusov reaction to give secondary phosphinic esters (6.227). With Grignard reagents, tertiary phosphines can be obtained (6.238-6.240). 

Phosphonic esters, ROPO(OR)2, react with allylic Grignard reagents to give the coupling product/ ... 

A less common approach to the synthesis of phosphinates is the reaction of electrophilic phosphonates with carbon nucleophiles such as Grignard reagents or lithium enolates. For example, the phosphinic acid analogue 71 of the amino acid statine was synthesized by displacement of tert-butyl lithioacetate on a 5-phenyl phosphonothioate 70 (Scheme 23)d104l The racemic diastereomers of the 5-phenyl phosphonothioate were obtained in pure form, and the displacement of the phenylsulfanyl moiety was found to be stereospecific, although the stereocenter at phosphorus would later be lost on hydrolysis of the ester. A similar displacement reaction has been described using the p h osp h on och I ori d ate.1711... 

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