Unsaturated fluorinated compounds, reduction

Homer-Wadsworth-Emons reaction (HWE reaction) of triethyl 2-fluorophos-ponoacetate 12 with an aldehyde stereoselectively yields an ( )-a-fluoro-a,p-unsaturated ester 13 [30], and it has been used to synthesize a fluorinated analog of natural compounds [31-33], Nagao et al. reported recently that the (Z)-isomer of a-fluoro-a,p-unsaturated ester 13 can be prepared stereoselectively by the reduction of triethyl 2-acyl-2-fluoro-2-phophonoacetate 14 with NaBHj at low temperature [34]. As the starting compound 14 can be prepared by the acylation of 12, both ( )- and (Z)-13 can be prepared from 12 stereoselectively [34] (Table 1). 

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