Gold-Catalyzed Regiodivergent [2 + 2 + 2]-Cycloadditions of Allenes with Triazines

Gold-catalyzed regiodivergent cycloadditions of functionalized allenes with 1,3,5-triazines, providing diverse N-heterocycles in moderate to excellent yields under mild reaction conditions, are reported. Importantly, different types of allenes exhibit distinct selectivity and reactivity for the reactions. Mechanistic investigations reveal that all of the cycloadditions proceed through a stepwise [2 + 2 + 2]-cycloaddition process

B(C₆F₅)₃‑Catalyzed Formal (<i>n</i> + 3) (<i>n</i> = 5 and 6) Cycloaddition of Bicyclo[1.1.0]butanes to Medium Bicyclo[<i>n</i>.1.1]alkanes

Herein, a B(C6F5)3-catalyzed formal (n + 3) (n = 5 and 6) cycloaddition of bicyclo[1.1.0]butanes (BCBs) with imidazolidines/hexahydropyrimidines is described. The reaction provides a modular, atom-economical, and efficient strategy to two libraries of synthetically challenging medium-bridged rings, 2,5-diazabicyclo[5.1.1]nonanes and 2,6-diazabicyclo[6.1.1]decanes, in moderate to excellent yields. This reaction also features simple operation, mild reaction conditions, and broad substrate scope. A scale-up experiment and various synthetic transformations of products further highlight the synthetic utility

B(C₆F₅)₃‑Catalyzed Formal (<i>n</i> + 3) (<i>n</i> = 5 and 6) Cycloaddition of Bicyclo[1.1.0]butanes to Medium Bicyclo[<i>n</i>.1.1]alkanes

Herein, a B(C6F5)3-catalyzed formal (n + 3) (n = 5 and 6) cycloaddition of bicyclo[1.1.0]butanes (BCBs) with imidazolidines/hexahydropyrimidines is described. The reaction provides a modular, atom-economical, and efficient strategy to two libraries of synthetically challenging medium-bridged rings, 2,5-diazabicyclo[5.1.1]nonanes and 2,6-diazabicyclo[6.1.1]decanes, in moderate to excellent yields. This reaction also features simple operation, mild reaction conditions, and broad substrate scope. A scale-up experiment and various synthetic transformations of products further highlight the synthetic utility

Synthesis of Polyheteroaromatic Compounds via Rhodium-Catalyzed Multiple C–H Bond Activation and Oxidative Annulation

Polyheteroaromatic compounds are potential optoelectronic conjugated materials due to their electro- and photochemical properties. Transition-metal-catalyzed multiple C–H activation and sequential oxidative annulation allows rapidly assembling of those compounds from readily available starting materials. A rhodium-catalyzed cascade oxidative annulation of β-enamino esters or 4-aminocoumarins with internal alkynes is described to access those compounds, featuring multiple C–H/N–H bond cleavages and sequential C–C/C–N bond formations in one pot

Stereodivergent Syntheses of N‑heterocycles by Catalyst-Controlled Reaction of Imidazolidines with Allenes

Reported herein is a catalyst-controlled reaction of imidazolidines with allenes, providing a general and efficient method to construct two series of N-heterocycles, 1,4-diazepanes via gold-catalyzed [5 + 2] cycloadditions and 1,4-diazabicyclo[4.3.1]decanes through iron-catalyzed [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades, in moderate to high yields under mild reaction conditions. Mechanistic investigations indicate that water acts as a proton shuttle to assist the [1,3]-hydrogen shift in the Friedel–Crafts cyclization process. This strategy features the use of imidazolidines as stable 1,5-dipoles for [5 + 2] cycloadditions and the utilization of an iron catalyst to accomplish the [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades in a highly diastereoselective manner for the synthesis of bridged-ring systems

Asymmetric (5 + 3) Annulation of Donor–Acceptor Cyclopropanes with Imidazolidines: Access to Saturated 1,4-Diazocanes

Saturated 1,4-diazocanes are highly important for medicinal chemistry and drug discovery, but their syntheses are often tedious. Herein, we report a copper-catalyzed (5 + 3) annulation of donor–acceptor cyclopropanes with imidazolidines, thereby providing a straightforward method to access a library of saturated 1,4-diazocanes in moderate to excellent yields under mild reaction conditions. More importantly, the asymmetric version of this (5 + 3) annulation leading to optically active saturated 1,4-diazocanes is achieved by two strategies: (i) chirality transfer and (ii) dynamic kinetic asymmetric transformation by employing copper triflate with an SaBOX ligand. In addition, the analogous (6 + 3) annulation of donor–acceptor cyclopropanes with hexahydropyrimidines is also realized

Stereodivergent Syntheses of N‑heterocycles by Catalyst-Controlled Reaction of Imidazolidines with Allenes

Reported herein is a catalyst-controlled reaction of imidazolidines with allenes, providing a general and efficient method to construct two series of N-heterocycles, 1,4-diazepanes via gold-catalyzed [5 + 2] cycloadditions and 1,4-diazabicyclo[4.3.1]decanes through iron-catalyzed [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades, in moderate to high yields under mild reaction conditions. Mechanistic investigations indicate that water acts as a proton shuttle to assist the [1,3]-hydrogen shift in the Friedel–Crafts cyclization process. This strategy features the use of imidazolidines as stable 1,5-dipoles for [5 + 2] cycloadditions and the utilization of an iron catalyst to accomplish the [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades in a highly diastereoselective manner for the synthesis of bridged-ring systems

Stereodivergent Syntheses of N‑heterocycles by Catalyst-Controlled Reaction of Imidazolidines with Allenes

Reported herein is a catalyst-controlled reaction of imidazolidines with allenes, providing a general and efficient method to construct two series of N-heterocycles, 1,4-diazepanes via gold-catalyzed [5 + 2] cycloadditions and 1,4-diazabicyclo[4.3.1]decanes through iron-catalyzed [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades, in moderate to high yields under mild reaction conditions. Mechanistic investigations indicate that water acts as a proton shuttle to assist the [1,3]-hydrogen shift in the Friedel–Crafts cyclization process. This strategy features the use of imidazolidines as stable 1,5-dipoles for [5 + 2] cycloadditions and the utilization of an iron catalyst to accomplish the [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades in a highly diastereoselective manner for the synthesis of bridged-ring systems

Stereodivergent Syntheses of N‑heterocycles by Catalyst-Controlled Reaction of Imidazolidines with Allenes

Reported herein is a catalyst-controlled reaction of imidazolidines with allenes, providing a general and efficient method to construct two series of N-heterocycles, 1,4-diazepanes via gold-catalyzed [5 + 2] cycloadditions and 1,4-diazabicyclo[4.3.1]decanes through iron-catalyzed [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades, in moderate to high yields under mild reaction conditions. Mechanistic investigations indicate that water acts as a proton shuttle to assist the [1,3]-hydrogen shift in the Friedel–Crafts cyclization process. This strategy features the use of imidazolidines as stable 1,5-dipoles for [5 + 2] cycloadditions and the utilization of an iron catalyst to accomplish the [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades in a highly diastereoselective manner for the synthesis of bridged-ring systems

Stereodivergent Syntheses of N‑heterocycles by Catalyst-Controlled Reaction of Imidazolidines with Allenes

Reported herein is a catalyst-controlled reaction of imidazolidines with allenes, providing a general and efficient method to construct two series of N-heterocycles, 1,4-diazepanes via gold-catalyzed [5 + 2] cycloadditions and 1,4-diazabicyclo[4.3.1]decanes through iron-catalyzed [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades, in moderate to high yields under mild reaction conditions. Mechanistic investigations indicate that water acts as a proton shuttle to assist the [1,3]-hydrogen shift in the Friedel–Crafts cyclization process. This strategy features the use of imidazolidines as stable 1,5-dipoles for [5 + 2] cycloadditions and the utilization of an iron catalyst to accomplish the [5 + 2] cycloaddition/Friedel–Crafts cyclization cascades in a highly diastereoselective manner for the synthesis of bridged-ring systems