Facile preparation of allenic hydroxyketones via rearrangement of propargylic alcohols

[GRAPHICS] Treatment of tertiary propargylic alcohols 13 with 3-diazo-2-butanone 6 and catalytic dirhodium tetraacetate in benzene gave good yields of the diaste reomeric allenic hydroxyketones 14, with, in some cases, good diastereocont rol. These products are presumably formed via the [2,3]-sigmatropic rearran gement of an alpha-propargyloxy enol derivative, This reaction has been ext ended to the preparation of homoallylic hydroxyketones from allylic alcohol s by reaction with 6 and the rhodium catalyst.