Ester Enolate Claisen Rearrangements of Allyl α-Fluoroacetates and α-Fluoropropanoates

Article abstract of DOI:10.1021/jo00001a065

The ester enolate Claisen rearrangement of allyl α-fluoroacetates 1 forms 2-fluoroalkenoic acids 2 in good to excellent yield with good internal asymmetric induction.This selectivity was unexpected as stereoselective deprotonation of fluoroacetates is not normally possible.The selective formation of the required α-fluoro silyl ketene acetal 3 was found to result from the stereoselective rearrangement of the allyl α-fluoro-α-silylacetate isomer.Although silyl ketene acetals derived from α-fluoropropanoates 7 also rearranged, control of internal asymmetric induction was not possible.