Search

Methods that can simultaneously install multiple different functional groups to heteroarenes via C−H functionalizations are valuable for complex molecule synthesis, which, however, remain challenging to realize. Here we report the development of vicinal di‐carbo‐functionalization of indoles in a site‐ and regioselective manner, enabled by the palladium/norbornene (Pd/NBE) cooperative catalysis. The reaction is initiated by the Pd(II)‐mediated C3‐metalation and specifically promoted by the C1‐substituted NBEs. The mild, scalable, and robust reaction conditions allow for a good substrate scope and excellent functional group tolerance. The resulting C2‐arylated C3‐alkenylated indoles can be converted to diverse synthetically useful scaffolds. The combined experimental and computational mechanistic study reveals the unique role of the C1‐substituted NBE in accelerating the turnover‐limiting oxidative addition step. [ABSTRACT FROM AUTHOR]

A new reaction mode of palladium/norbornene (Pd/NBE) cooperative catalysis is reported involving the selective coupling of two different carbon‐based electrophiles for vicinal double C‐H functionalization of five‐membered heteroarenes in a site‐selective and redox‐neutral manner. The key is to use alkynyl bromides as the second electrophile, which allows vicinal difunctionalization of a wide range of heteroarenes including pyrroles, thiophenes and furans at their C4 and C5 positions. One‐ or two‐step tetrafunctionalizations of simple pyrrole and thiophene have also been realized. The C2‐substituted NBEs prove most effective in these reactions, and the mechanistic exploration discloses the origin of the high selectivity of this transformation. Synthetic utility of this method has been exemplified in the concise preparations of thiophene‐containing organic materials and a protein kinase inhibitor analogue. Preliminary success has also been achieved in a direct annulation event, using a tethered ketone as the second electrophile. [ABSTRACT FROM AUTHOR]

Abstract: Herein we report a direct annulation between aryl iodides and epoxides through palladium/norbornene (Pd/NBE) cooperative catalysis. An iso‐propyl ester substituted NBE was found to be most efficient to suppress the formation of multiple‐NBE‐insertion byproducts and affords the desired 2,3‐dihydrobenzofuran derivatives in 44–99 % yields. The reaction is scalable and tolerates a range of functional groups. Asymmetric synthesis is realized using an enantiopure epoxide. Application of this method into a concise synthesis of insecticide fufenozide is demonstrated. [ABSTRACT FROM AUTHOR]

An efficient ruthenium(II)-catalyzed oxidative annulation reaction of various arylimidazolium salts with alkynes via N-heterocyclic carbene-directed C--H activation to obtain substituted benzo[ ij]imidazo[2,1,5-de]quinolizinium salts is reported. This catalytic reaction proceeds in an excellent regioselective manner when using unsymmetrical alkynes as reactants. The intermediate mono-annulated products can be obtained by reducing the amount of catalyst. Two catalytically competent Nheterocyclic carbene-based cyclometallated ruthenium( II) complexes have been isolated and characterized, which represent the key intermediates in the catalytic cycle. Moreover, most of the products show a strong fluorescent property, indicating their potential for making new light-emitting materials. [ABSTRACT FROM AUTHOR]

An efficient ruthenium(II)-catalyzed oxidative annulation reaction of various arylimidazolium salts with alkynes via N-heterocyclic carbene-directed C-H activation to obtain substituted benzimidazoquinolizinium salts is reported. [ABSTRACT FROM AUTHOR]

The article presents chemical equations related to the article "Rhodium(III)-Catalyzed Intermolecular Amidation with Azides via C(sp3)?H Functionalization" by N. Wang, R. Li, and others, published in the periodical "Journal of Organic Chemistry" in 2014.