Generation and trapping of allene oxides: An approach to chiral, nonracemic α-alkoxyketones

Article abstract of DOI:10.1016/S0040-4020(98)00878-3

Epoxy mesylates 5 react with a variety of sodium alkoxides to produce the corresponding α-alkoxyketones in good yields. Evidence is presented for the involvement of transient allene oxides in these reactions. Enantiomerically enriched epoxy mesylates (2R,3S)-5a-c were prepared using the Sharpless asymmetric epoxidation reaction as the key step. These precursors rearrange to α-alkoxyketones without significant racemisation under modified reaction conditions (ROK, 18-crown-6, THF, -78°C). The reactions are shown to proceed with stereochemical inversion at the epoxide centre.