Synthesis and Reactions of Phosphonate Anions

The Horner-Wadsworth-Emmons reaction between bis(benzyloxy)benzalde-hydes and an ester-substituted benzylphosphonate or triethylphosphonoacetate, yield the correponding stilbene or cinnamate derivatives, respectively. These are crucial steps in the synthesis of chiral AB2 monomers which are themselves valuable dendrimer precursors. Standard Horner-Wadsworth-Emmons reactions between P-ketophosphonates and aldehydes have been used in the synthesis 

Ethyl phosphonoacetate reacts with 3-keto-substituted thiophenes to give 81 which are precursors to bridged dithienylethylenes such as 82. The synthesis of a-ylidene-y-amidobutyronitriles, RCONH(CH2)2C(CN) = CR R (R = NPh2, r2 = R rz Me R = R = Ph, R = H, Me, Ph), has been achieved by the reaction of the phosphonates RC0NH(CH2)2CHCNP(0)(0Et)2 (R = NPh2, Ph) with ketones. The enantioselective synthesis of allenecarboxylates is accomplished by asymmetric Homer-Wadsworth-Emmons reaction of chiral phosphonoacetate- 

Treatment of diethyltrichloromethylphosphonate with butyllithium followed by an aldehyde or cycloalkenone leads to a-chlorovinylphosphonates (89). Pyranosic 3,4-enuloses exhibit anomalous behaviour when treated with the enolate of dimethyl(methoxycarbonyl)-methylphosphonate, leading to phos-phorylated products. The synthesis of a-(alkyl)methylene-Y-iodo-Y-butyrolac-tones has been accomplished in high yields, but with poor selectivity, from the reaction of a-phosphono-y-iodo-Y-butyrolactones and aldehydes.  

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