Several α-fluorovinylphosphonates (6) have been synthesised from the Peterson olefination reaction applied to both aldehydes and ketones in conjunction with α-lithiated-α-fluoro-α- trimethylsilylmethylphosphonate (2). The reaction with aldehydes gives mainly the E-isomer whereas reaction with ketones gives mainly the Z-isomer. We propose a closed transition state to explain the results of our study.
