Nickel Chain-Walking Catalysis: A Journey to Migratory Carboboration of Alkenes

Abstract

Conspectus Chain-walking offers extensive opportunities for innovating synthetic methods that involve constructing chemical bonds at unconventional sites. This approach provides previously inaccessible retrosynthetic disconnections in organic synthesis. Through chain-walking, transition metal-catalyzed alkene difunctionalization reactions can take place in a 1,n-addition (n ≠ 2) mode. Unlike classical 1,2-regioselective difunctionalization reactions, there remains a scarcity of reports regarding migratory patterns. Moreover, the range of olefins utilized in these studies is quite limited. About five years ago, our research group embarked on a project aimed at developing valuable migratory difunctionalization reactions of alkenes through chain-walking. Our focus was on carboboration of alkenes utilizing nickel catalysis. The reaction commences with the migratory insertion of an olefin into a Ni–Bpin species. Subsequently, a thermodynamically stable alkyl nickel complex is generated through a chain-walking process. This complex then couples with a carbon-based electrophile, leading to the formation of an alkylboron compound. It is worth highlighting that the success of these transformations relies significantly on the utilization of a bisnitrogen-based ligand and LiOMe as a B2pin2 activator. Synthetically, these migratory carboboration reactions establish a robust platform for the rapid and efficient synthesis of a wide range of structurally diverse organoboron compounds, which are not facially accessed by conventional methods. The incorporation of a versatile boron group introduces a wealth of possibilities for subsequent diversifications, significantly enhancing the value of the resulting products and allowing for the creation of a broader range of valuable derivatives and applications. This Account provides a comprehensive overview of our research efforts and advancements in the field of migratory carboboration of unactivated alkenes using nickel catalysis. We begin by outlining the development of a series of 1,1-regioselective carboboration reactions of terminal alkenes. A significant focus is placed on the initial integration of boronate, which not only triggers the formation of thermodynamically stable metal species but also exerts control over remote stereochemistry in reactions involving substituted methylenecyclohexenes. Continuing our exploration, remarkable success is achieved in 1,3-regio- and cis-stereoselectivity when dealing with cyclic alkenes. Remarkably, nickel chain-walking catalysis enables heterocyclic alkenes to be viable coupling partners within our transformations. Moreover, it grants us the ability to achieve regioselectivity for cyclohexenes that was previously unattainable, thus expanding the horizons of regiochemical control in these reactions. Lastly, we present the evolution of ligand-modulated regiodivergent carboboration of allylarenes. By gaining insights into the underlying mechanisms driving regiodivergence, we lay a strong foundation for tackling challenges related to selecting s...

Nickel-Catalyzed Mono- and Dihydrosilylation of Aliphatic Alkynes in Aqueous and Aerobic Conditions

“…Along with n -decyl-substituted alkyne 1a , alkyne 1b with a bulky cyclohexyl substituent was transformed into disilane 5b in an 89% yield. The introduction of a silyl group at the benzylic position of alkyne 1c through nickel chain-walking catalysis was not observed, and the desired disilane 5c was obtained in an 89% yield. Alkynes with ester ( 1d ), silyl ether ( 1e ), and sulfonate ( 1f ) were smoothly converted to the corresponding disilanes ( 5d – 5f ) in 97–98% yields with complete functional-group tolerance.…”

Ni-catalysed acceptorless dehydrogenative aromatisation of cyclohexanones enabled by concerted catalysis specific to supported nanoparticles

“…1c) [38][39][40][41] . Second, the fast migratory insertion of hydride species on the Ni centre into alkene species [42][43][44] before H 2 evolution inhibits the formation of dehydrogenated products (Fig. 1c).…”

Regio- and Diastereoselective Highly Strained Alkylidenecyclobutane Isomerization/Hydroacylation: Synthesis of Multisubstituted Cyclobutanes with Consecutive Stereocenters

“…Transition metal-catalyzed alkene isomerization in combination with subsequent chemical transformations opens an exquisite and powerful avenue for the construction of synthetically valuable substances, undoubtedly impressing organometallic chemists with its inherent redox-, atom-, and step-economy profiles . The well-accepted mechanism involves either an iterative migratory insertion/β-H elimination process or the intermediacy of an allylmetal species derived from abstraction of the allylic hydrogen .…”

“…The well-accepted mechanism involves either an iterative migratory insertion/β-H elimination process or the intermediacy of an allylmetal species derived from abstraction of the allylic hydrogen . Besides the advantage of enabling the activation of the distal C–H bond, the chemical outcome of such a “chain-walking” process is not usually susceptible to the position and geometry of the double bond and has been widely applied in the remote functionalization of acyclic alkenes (Scheme A). , Over the past few decades, substantial advancements have been made in the isomerization/functionalization of cyclic alkenes, which primarily focused on low-strained five- or six-membered ring systems and the “endo to endo” isomerization of endocyclic double bonds (Scheme B, a) . Nevertheless, the synthetic challenges associated with the isomerization of exocyclic double bonds into endocyclic double bonds have limited the achievement of remote functionalization and, therefore, only a few reports have successfully demonstrated this “exo to endo” approach in low-strained ring systems (Scheme B, b) .…”