Dimeric Manganese‐Catalyzed Hydroalkenylation of Alkynes with a Versatile Silicon‐Based Directing Group

Herein, we present a manganese‐catalyzed, branched‐selective hydroalkenylation of terminal alkynes, under mild conditions through facile installation of a versatile silanol as a removable directing group. With an alkenyl boronic acid as the coupling partner, this reaction produces stereodefined (E,E)‐1,3‐dienes with high regio‐, chemo‐ and stereoselectivity. The protocol features mild reaction conditions such as room temperature and an air atmosphere, while maintaining excellent functional group compatibility. The resulting 1,3‐dienesilanol products serve as versatile building blocks, as the removal of the silanol group allows for the synthesis of both branched terminal 1,3‐dienes for downstream coupling reactions, as well as stereoselective construction of linear (E,E)‐1,3‐dienes and (E,E,E)‐ or (E,E,Z)‐1,3,5‐trienes. In addition, a Diels–Alder cycloaddition can smoothly and selectively deliver silicon‐containing pentasubstituted cyclohexene derivatives. Mechanistic investigations, in conjunction with DFT calculations, suggest a bimetallic synergistic activation model to account for the observed enhanced catalytic efficiency and good regioselectivity. The use of silanol as a removable directing group allows for dimeric manganese‐catalyzed selective hydroalkenylation of alkynes at ambient conditions under an open air atmosphere. The resulting stereodefined 1,3‐diene silanol products are obtained in good regio‐, chemo‐ and stereo‐selectivity while also being versatile building blocks for rich downstream transformations.