Cobalt-Catalyzed Regio- and Stereoselective Hydrosilylation of Alk-2-ynes with Tertiary Silanes

Selectivity control in the addition reactions of internal alkynes that bear two similar substituents presents a big challenge in modern organic synthesis. Herein we report that β-(E)-selective hydrosilylation of alk-2-ynes with tertiary silanes can be achieved by using Co2(CO)8 as the catalyst. Under the catalytic reaction conditions, a wide range of alk-2-ynes can be converted into vinylsilanes with the β-(E) isomers as the major or sole hydrosilylation products. Mechanistic studies suggest that alkyne-bridged dicobalt species are the likely intermediates. Steric repulsion between substituents in alkenyl-bridged dicobalt silyl intermediates is proposed as the key factor inducing the observed regioselectivity.