Diborodichloromethane as Versatile Reagent for Chemodivergent Synthesis of gem-Diborylalkanes

Electrochemistry-Enabled C-Heteroatom Bond Formation of Alkyl Germanes

Because of their robustness and orthogonal reactivity features, alkyl germanes bear significant potential as functional handles for the construction of C(sp3)-rich scaffolds, especially in the context of modular synthetic approaches. However, to date, only radical-based reactivity has been accessible from these functional handles, which limits the types of possible decorations. Here, we describe the first general C(sp3)-heteroatom bond formation of alkyl germanes (-GeEt3) by leveraging electrochemistry to unlock polar reactivity. This approach allowed us to couple C(sp3)-GeEt3 with a variety of nucleophiles to construct ethers, esters, amines, amides, sulfonamides, sulfides, as well as C-P, C-F, and C-C bonds. The compatibility of the electrochemical approach with a modular synthetic strategy of a C1 motif was also showcased, involving the sequential functionalization of Cl, Bpin, and ultimately GeEt3 via electrochemistry.

Mechanochemical Synthesis of α-halo Alkylboronic Esters

α-halo alkylboronic esters, acting as ambiphilic synthons, play a pivotal role as versatile intermediates in fields like pharmaceutical science and organic chemistry. The sequential transformation of carbon-boron and carbon-halogen bonds into a broad range of carbon-X bonds allows for programmable bond formation, facilitating the incorporation of multiple substituents at a single position and streamlining the synthesis of complex molecules. Nevertheless, the synthetic potential of these compounds is constrained by limited reaction patterns. Additionally, the conventional methods often necessitate the use of bulk toxic solvents, exhibit sensitivity to air/moisture, rely on expensive metal catalysts, and involve extended reaction times. In this report, a ball milling technique is introduced that overcomes these limitations, enabling the external catalyst-free multicomponent coupling of aryl diazonium salts, alkenes, and simple metal halides. This approach offers a general and straightforward method for obtaining a diverse array of α-halo alkylboronic esters, thereby paving the way for the extensive utilization of these synthons in the synthesis of fine chemicals.

Dinuclear gold-catalyzed divergent dechlorinative radical borylation of gem-dichloroalkanes

The enormous and widespread use of organoboronic acids has prompted the development of innovative synthetic methodologies to meet the demands on structural diversity and functional group tolerance. The existing photoinduced defunctionalization radical borylation, typically focused on the conversion of one C-X bond (X= Br, I, or other leaving group) into only one C-B bond. Herein, we disclose a divergent radical dechloroborylation reaction enabled by dinuclear gold catalysis with visible light irradiation. A wide range of structurally diverse alkyl boronic, α-chloroboronic, and gem-diboronic esters can be synthesized in moderate to good yields (up to 92%). Its synthetic robustness is further demonstrated on a preparative scale and applied to late-stage diversification of complex molecules. The process hinges on a C-Cl bond relay activation in readily available gem-dichloroalkanes through inner-sphere electron transfer, overcoming the redox potential limits of unreactive alkyl chlorides.

Palladium-Catalyzed Cascade Heck Coupling and Allylboration of Iododiboron Compounds via Diboryl Radicals

Geminal bis(boronates) are versatile synthetic building blocks in organic chemistry. The fact that they predominantly serve as nucleophiles in the previous reports, however, has restrained their synthetic potential. Herein we disclose the ambiphilic reactivity of α-halogenated geminal bis(boronates), of which the first catalytic utilization was accomplished by merging a formal Heck cross-coupling with a highly diastereoselective allylboration of aldehydes or imines, providing a new avenue for rapid assembly of polyfunctionalized boron-containing compounds. We demonstrated that this cascade reaction is highly efficient and compatible with various functional groups, and a wide range of heterocycles. In contrast to a classical Pd(0/II) scenario, mechanistic experiments and DFT calculations have provided strong evidence for a catalytic cycle involving Pd(I)/diboryl carbon radical intermediates.

α-Boryl Carbanions: The Influence of Geminal Heteroatoms in C-C Bond Formation

The wide applications of alpha-boryl carbanions in selective coupling with organohalides, imines/carbonyls and conjugated unsaturated substrates has become an interesting tool for organic synthesis. Strategically, the inclusion of heteroatoms, such as Si, S, N, F, Cl, Br and I in the alpha position opens a new venue towards multifunctionalities in molecular design. Here, a conceptual and practical view on powerful carbanions, containing α-silicoboron, α-thioboron, α-haloboron and α-aminoboron is given, as well as a prespective on their efficient application for selective electrophilic trapping.