The chemistry of organoborates. 9. A regiospecific and highly stereoselective construction of trisubstituted αβ-unsaturated ketones, tetrasubstituted αβ-unsaturated ketones and specifically protected 1,3-diketones from alkynyltrialkylborates

Article abstract of DOI:10.1016/0040-4020(94)00953-R

Lithium alkynyltrialkylborates react with dioxolanium fluorosulphonates in a highly stereoselective fashion such that the dioxolanium group and the migrating group and the migrating group are on the same side of the new alkene intermediate. Hydrolysis of the intermediate yields Z-trisubstituted αβ-unsaturated ketones in which all three substituents have different origins and can be independently varied. Oxidation of the intermediates gives β-ketoacetals, which are regiospecifically protected 1,3-diketones. If the initial intermediates are allowed to stand, then another migration occurs and tetra-substituted αβ-unsaturated ketones result.