Qing Qing Cheng

Copper-Catalyzed B–H Bond Insertion Reaction: A Highly Efficient and Enantioselective C–B Bond-Forming Reaction with Amine–Borane and Phosphine–Borane Adducts

A copper-catalyzed B-H bond insertion reaction with amine- and phosphine-borane adducts was realized with high yield and enantioselectivity under mild reaction conditions. The B-H bond insertion reaction provides a new C-B bond-forming methodology and an efficient approach to chiral organoboron compounds.

Lewis Acid/Rhodium-Catalyzed Formal [3 + 3]-Cycloaddition of Enoldiazoacetates with Donor–Acceptor Cyclopropanes

A formal [3 + 3]-cycloaddition of enoldiazoacetates with donor-acceptor cyclopropanes was realized by the combination of a Lewis acid-catalyzed diastereoselective [3 + 2]-cycloaddition and a subsequent rhodium-catalyzed chemoselective ring expansion. This tandem transformation provides an efficient approach to highly functionalized cyclohexenes.

Copper-Catalyzed Divergent Addition Reactions of Enoldiazoacetamides with Nitrones

Catalyst-controlled divergent addition reactions of enoldiazoacetamides with nitrones have been developed. By using copper(I) tetrafluoroborate/bisoxazoline complex as the catalyst, a [3+3]-cycloaddition reaction was achieved with excellent yield and enantioselectivity under exceptionally mild conditions, which represents the first highly enantioselective base-metal-catalyzed vinylcarbene transformation. When the catalyst was changed to copper(I) triflate, Mannich addition products were formed in high yields with near exclusivity under otherwise identical conditions.

Dirhodium(II)-Catalyzed Annulation of Enoldiazoacetamides with α-Diazoketones: An Efficient and Highly Selective Approach to Fused and Bridged Ring Systems

A dirhodium(II)-catalyzed annulation reaction between two structurally different diazocarbonyl compounds furnishes the donor-acceptor cyclopropane-fused benzoxa[3.2.1]octane scaffold with excellent chemo-, regio-, and diastereoselectivity under exceptionally mild conditions. The composite transformation occurs by [3+2]-cycloaddition between donor-acceptor cyclopropenes generated from enoldiazoacetamides and carbonyl ylides formed from intramolecular carbene-carbonyl cyclization in one pot with one catalyst. The annulation products can be readily transformed into benzoxa[3.3.1]nonane and hexahydronaphthofuran derivatives with exact stereocontrol. This method allows the efficient construction of three fused and bridged ring systems, all of which are important skeletons of numerous biologically active natural products.

Highly Regio- and Enantioselective Formal [3 + 2]-Annulation of Indoles with Electrophilic Enol Carbene Intermediates

Chiral cyclopentane-fused indolines are synthesized with high regio- and enantiocontrol by formal [3 + 2]-annulation reactions of indoles and electrophilic enol carbenes. High enantioselectivity and exclusive regiocontrol occurred with enoldiazoacetamides using a less sterically encumbered prolinate-ligated dirhodium(II) catalyst in reactions with N-substituted indoles without substituents at the 2- or 3-positions via a selective vinylogous addition process. In this transformation, donor-acceptor cyclopropenes generated from enoldiazoacetamides serve as the carbene precursors to form metal carbene intermediates.

Divergent Rhodium-Catalyzed Cyclization Reactions of Enoldiazoacetamides with Nitrosoarenes

The first cyclization reactions of enoldiazo compounds with nitrosoarenes have been developed. Under the catalysis of rhodium(II) octanoate, [3 + 2]-cyclization between enoldiazoacetamides and nitrosoarenes occurred through cleavages of the enol double bond and the amide bond, thus furnishing fully substituted 5-isoxazolone derivatives. Upon changing the catalyst to rhodium(II) caprolactamate, the reaction pathway switched to an unprecedented formal [5 + 1]-cyclization that provided multifunctionalized 1,3-oxazin-4-ones with near exclusivity under otherwise identical conditions. Mechanistic studies uncovered distinct catalytic activities and reaction intermediates, which plausibly rationalized the novel reactivity and catalyst-controlled chemodivergence. Furthermore, a mechanism-inspired enantioselective rhodium-catalyzed reaction of γ-substituted enoldiazoacetamide with nitrosobenzene produced highly enantioenriched heterocycle-linked trialkylamine.

Vinyldiazo Reagents and Metal Catalysts: A Versatile Toolkit for Heterocycle and Carbocycle Construction

Over the past decade, vinyldiazo compounds have provided mild, efficient, and highly selective methods for the construction of heterocycles and carbocycles. Dinitrogen extrusion with suitable catalysts provides the carbon framework for [3+n] cycloaddition with a large variety of dipolarophiles. This minireview, covering the latest achievements in the field of metal‐catalyzed cyclization reactions with vinyldiazo reagents, focuses on reagent‐ or catalyst‐dependent chemodivergence: different vinyldiazo reagents or metal catalysts direct reactions to different cyclization pathways that give different reaction outcomes. Accordingly, metal‐catalyzed cyclization reactions of vinyldiazo compounds with nitrosoarenes, nitrones, indoles, and other diazo compounds are chosen to showcase the controllable versatility of the combination of vinyldiazo reagents and metal catalysts.