Nickel-Mediated Three-Component Cycloaddition Reaction of Carboryne, Alkenes, and Alkynes

Abstract

Transition metal mediated multicomponent cross-coupling reactions are a powerful strategy to assemble complex molecules from very simple precursors in a single operation. This Communication reports a nickel-mediated three-component cycloaddition reaction of carboryne with alkenes and alkynes giving dihydrobenzocarborane derivatives with excellent chemo- and regioselectivity. A reaction mechanism involving sequential alkene and alkyne insertion, followed by reductive elimination, is proposed. The key intermediate of nickelacyclopentane was isolated and confirmed by single-crystal X-ray analyses. This work furnishes a new method for the preparation of substituted dihydrobenzocarboranes that are difficult to obtain by other methods.

Three‐Component [2+2+2] Cycloaddition of Carboryne, Unactivated Alkene, and Alkyne via Zirconacyclopentane Mediated by Nickel: One‐Pot Synthesis of Dihydrobenzocarboranes

“…[3] In the presence of a nickel complex, carboryne can undergo, in a controlled manner, coupling reaction with alkenes to generate alkenyl carboranes, [4] two-component [2+2+2] cycloaddition with two equivalents of alkynes to afford benzocarboranes, [5] and three-component [2+2+2] cyclotrimerization with activated alkene and alkyne to give dihydrobenzocarboranes. [6] In the latter case, activated alkenes such as methyl acrylate and 2-vinylpyridine must be employed, because they are more reactive than alkynes in the system and the donor atom of the olefin can stabilize the intermediate by intramolecular coordination, thereby preventing the b-H elimination and making the subsequent alkyne insertion possible to realize the three-component cycloaddition. However, attempts to achieve nickel-mediated selective cycloaddition of carboryne with unactivated alkene and alkyne have not been successful to date but gave a mixture of alkenyl carboranes and benzocarboranes.…”

Reactivity differences between nickel and palladium complexes bearing 1,2-diphosphino-1,2-dicarba-dodecaborane ligand

“…Supplementary data CCDC reference numbers 761994 (2), 761995 (4), 761996 (5), 761997 (6), 761998 (7), 761999 (8) and 762000 (9); contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif.…”

Recent developments in homobimetallic reagents and catalysts for organic synthesis

“…Based on this discovery, nickel-mediated 3-component cycloaddition reactions of the carboryne with alkenes and alkynes through intermediate 20 afforded dihydrobenzocarborane derivatives with excellent chemo-and regioselectivity [25]. Treatment of Cp 2 ZrCl 2 with 1 equivalent of Li 2 C 2 B 10 H 10 in Et 2 O at room temperature for 1 h gave a novel zirconocenecarboranyl complex (21 in Scheme 5) [26].…”