摘要：

Diethyl (fluorocarbethoxymethyl)phosphonate (1), prepared from triethyl phosphite and ethyl bbromofluoroacetate, reacts with n-butyllithium in THF to give the phosphonate carbanion 2. Addition of the pregenerated carbanion 2 to a THF solution of methyl or ethyl oxalyl chloride at -78 degrees C forms the acylated phosphonate (EtO)(2)P(O)CF(COCO(2)R)CO(2)Et (3). In situ reaction of 3 with Grignard reagents affords alpha-fluoro-alpha,beta-unsaturated diesters R'(CO(2)R)C=CFCO(2)Et in moderate to good yields with high E-stereoselectivity. The reaction is applicable to primary, secondary, and tertiary alkyl, alkenyl, alkynyl, aryl, cyclohexyl, and perfluorinated Grignard reagents. The assignment of E and Z configuration is based on NOE experiment. The E/Z ratio of unsaturated diesters formed in the reaction varies with the metal ion and cosolvent. However, solvents and bases have little influence on the stereoselectivity.

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