Regio- and Stereoselective <i>anti</i>-Hydroalumination of Internal and Terminal Alkynes Using a Mixed Reagent of Cesium Fluoride with Diisobutylaluminum Hydride

We revealed that a mixed reagent of cesium fluoride with diisobutylaluminum hydride (CsF-DIBAL-H) is valuable for the <i>anti</i>-hydroalumination of 1-arylalk-1-ynes with complete regioselectivity toward the formation of 1-arylalk-1-enylalanes. The hydroalumination of internal alkynes with CsF-DIBAL-H followed by hydrolysis gave (<i>E</i>)-alkenes with a high stereoselectivity. It was also revealed that the reaction of terminal arylalkynes with CsF-DIBAL-H provided alkenylalanes in a Markovnikov manner. This hydroalumination apparently exhibited inverse selectivity to the conventional hydroalumination of diisobutylaluminum hydride.