Practical Synthesis of Chiral Allylboronates by Asymmetric 1,1‐Difunctionalization of Terminal Alkenes

Enantioselective Ni-Catalyzed 1,2-Borylalkynylation of Unactivated Alkenes

Enantioselective three-component difunctionalization of alkenes with boron reagents represents an attractive strategy for assembling three-dimensional chiral organoboron compounds. However, regio- and enantiocontrol comprise the pivot challenges in these transformations, which predominantly require the use of activated conjugated alkenes. Herein, by utilizing various carbonyl directing groups, including amides, sulfinamides, ketones, and esters, we succeed in realizing a nickel-catalyzed 1,2-borylalkynylation of unactivated alkenes to enable the simultaneous incorporation of a boron entity and an sp-fragment across the double bond. The products contain boryl, alkynyl, and carbonyl functional groups with orthogonal synthetic reactivities, offering three handles for further derivatization to access valuable intermediates. The utility of this ligand-enabled asymmetric protocol has been highlighted through the late-stage decoration of drug-relevant molecules.

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

ConspectusChain-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 specific sites in chain-walking reactions, especially when dealing with multiple stable factors. We anticipate that our findings, coupled with the mechanistic insights we've gained, will not only advance the realm of nickel chain-walking catalysis but also contribute to the broader understanding of selectivity control in reactions of this nature. This advancement will also catalyze the synthesis of intricate functional molecules, contributing to the creation of complex and valuable compounds in the realm of organic chemistry.

Base-Modulated 1,3-Regio- and Stereoselective Carboboration of Cyclohexenes

While chain-walking stimulates wide interest in both polymerization and organic synthesis, site- and stereoselective control of chain-walking on rings is still a challenging task in the realm of organometallic catalysis. Inspired by a controllable chain-walking on cyclohexane rings in olefin polymerization, we have developed a set of chain-walking carboborations of cyclohexenes based on nickel catalysis. Different from the 1,4-trans-selectivity disclosed in polymer science, a high level of 1,3-regio- and cis-stereoselectivity is obtained in our reactions. Mechanistically, we discovery that the base affects the reduction ability of B2 pin2 and different bases lead to different catalytic cycles and different regioselective products (1,2- Vs 1,3-addition). This study provides a concise and modular method for the synthesis of 1,3-disubstituted cyclohexylboron compounds. The incorporation of a readily modifiable boronate group greatly enhances the value of this method, the synthetic potential of which was highlighted by the synthesis of a series of high-valued commercial chemicals and pharmaceutically interesting molecules.

Stereoselective Synthesis of Multisubstituted Alkenes via Ruthenium-Catalyzed Remote Migration Arylation of Nonactivated Olefins

Polysubstituted alkenes are an important class of organic intermediates that widely exist in various natural products and drug molecules. Herein, we reported a stereoselective synthesis of multisubstituted alkenes via ruthenium-catalyzed remote migration arylation of nonactivated olefins. This strategy exhibited wide substrate suitability and excellent functional group tolerance. In addition, we demonstrated the indispensable role of two types of ruthenium through mechanism experiments.

Nickel-Catalyzed 1,1-Aminoborylation of Unactivated Terminal Alkenes

Herein, we disclose a Ni-catalyzed 1,1-difunctionalization of unactivated terminal alkenes that enables the incorporation of two different heteroatom motifs across an olefin backbone, thus streamlining the access to α-aminoboronic acid derivatives from simple precursors. The method is characterized by its simplicity and generality across a wide number of coupling counterparts.

A General Strategy for the Asymmetric Preparation of α-Stereogenic Allyl Silanes, Germanes, and Boronate Esters via Dual Copper Hydride- and Palladium-Catalysis

α-Stereogenic allyl metalloids are versatile synthetic intermediates which can undergo various stereocontrolled transformations. Most existing methods to prepare α-stereogenic allyl metalloids involve multi-step sequences that curtail the number of compatible substrates and are limited to the synthesis of boronates. Here, we report a general method for the enantioselective preparation of α-stereogenic allyl metalloids utilizing dual CuH- and Pd-catalysis. This approach leverages a stereoretentive Cu-to-Pd transmetalation of an in situ generated alkyl copper species to allow access to enantioenriched allyl silanes, germanes, and boronate esters with broad functional group compatibility.