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

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

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 <i>N</i>-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

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

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

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