Stereoselective Coupling of (Alkynyl acetal)Co2(CO)6 with Enol Silanes

Article abstract of DOI:10.1021/jo00288a031

Dicobalt hexacarbonyl complexes of acetylenic acetals 2 react with enol silanes in the presence of BF3*Et2O to afford β-alkoxyacetylenic ketone derivatives in excellent yield and modest to excellent syn stereoselectivity.The stereochemistry of the diastereomeric products is readily established by 1H NMR and has been confirmed in one case by X-ray diffraction.In contrast, the corresponding reaction of a noncomplexed acetylenic acetal proceeds with no stereoselectivity.Demetalation of the diastereomeric product complexes provides isomerically pure β-alkoxy-γ-acetylenic ketones.