REACTIONS OF TRIALKYLALKYNYLBORATES WITH 2-ALKYL-1,3-DIOXALAN-2-YLIUM FLUOROSULPHONATES. VERSATILE DIRECT ROUTES TO Z-αβ-UNSATURATED KETONES, SPECIFICALLY PROTECTED 1,3-DIKETONES AND OTHER KETONIC SPECIES.

Article abstract of DOI:10.1016/S0040-4039(00)84416-0

The reactions of 2-alkyl-1,3-dioxolan-2-ylium fluorosulphonates with trialkylalkynylborates proceed at the β-position of the alkynylborates and may be controlled to give either one or two migrations from boron to carbon.The one migration is stereospecific and the products on hydrolysis yield Z-αβ-unsaturated ketones, whilst oxidation gives specifically mono-protected 1,3-diketones.If the reactions are allowed to proceed for a longer time, then a second migration from boron to carbon occurs to yield intermediates that give other αβ-unsaturated ketones on oxidation.