Transition-Metal-Free -Diarylations to Reach All-Carbon Quaternary Centers.

Herein, we disclose a convenient protocol for the α-diarylation of carbon nucleophiles to yield heavily functionalized quaternary products. Diaryliodonium salts are utilized to transfer both aryl groups under transition-metal-free conditions, which enables an atom-efficient and high-yielding method with broad functional group tolerance. The methodology is amenable to a wide variety of carbon nucleophiles and can be utilized in late-stage functionalization of complex arenes.

Transition-Metal-Free Difunctionalization of Sulfur Nucleophiles.

Efficient protocols for accessing iodo-substituted diaryl and aryl(vinyl) sulfides have been developed using iodonium salts as reactive electrophilic arylation and vinylation reagents. The reactions take place under transition-metal-free conditions, employing odorless and convenient sulfur reagents. A wide variety of functional groups are tolerated in the S-diarylation, enabling the regioselective late-stage application of several heterocycles and drug molecules under mild reaction conditions.

Regioselective and Redox-Neutral Cp*Ir -Catalyzed Allylic C-H Alkynylation.

Herein, we report a Cp*Ir -catalyzed highly regioselective and redox-neutral protocol for the construction of 1,4-enynes from unactivated olefins and bromoalkynes via intermolecular allylic C-H alkynylation. The developed mild reaction conditions tolerate a broad range of common functional groups, even enabling selective alkynylation of allylic C-H bonds in the presence of other prominent directing groups. Mechanistic experiments including the isolation of a catalytically active Ir -allyl species support an intermolecular allylic C-H activation followed by an electrophilic alkynylation.

Intermolecular 1,4-Carboamination of Conjugated Dienes Enabled by Cp*Rh -Catalyzed C-H Activation.

A protocol for the three-component 1,4-carboamination of dienes is described. Synthetically versatile Weinreb amides were coupled with 1,3-dienes and readily available dioxazolones as the nitrogen source using [Cp*RhCl ] -catalyzed C-H activation to deliver the 1,4-carboaminated products. This transformation proceeds under mild reaction conditions and affords the products with high levels of regio- and E-selectivity.

Site-selective C-H activation and regiospecific annulation using propargylic carbonates.

Herein we describe an unprecedented Ru-catalyzed site-selective and regiospecific annulation of benzoic acids with propargylic carbonates. The weakly coordinating carboxylic acid moiety outperformed other typically used directing groups in C-H activation, including ketone, nitrile, sulfonamide, amide and strongly coordinating nitrogen heterocycles. This is an important step towards the application of C-H activation reactions in complex (functional) real-world molecules.

Intermolecular, Branch-Selective, and Redox-Neutral Cp*Ir -Catalyzed Allylic C-H Amidation.

Herein, we report the redox-neutral, intermolecular, and highly branch-selective amidation of allylic C-H bonds enabled by Cp*Ir catalysis. A variety of readily available carboxylic acids were converted into the corresponding dioxazolones and efficiently coupled with terminal and internal olefins in high yields and selectivities. Mechanistic investigations support the formation of a nucleophilic Ir -allyl intermediate rather than the direct insertion of an Ir-nitrenoid species into the allylic C-H bond.

Stereoselective Construction of Pyrazinoindoles and Oxazinoindoles via Ring-Opening/Pictet-Spengler Reaction of Aziridines and Epoxides with 3-Methylindoles and Carbonyls.

A highly efficient and stereoselective route to access 1,3-disubstituted 1,2,3,4-tetrahydropyrazino[1,2- a]indoles and 3,4-dihydro-1H-[1,4]oxazino[4,3- a]indoles with excellent stereoselectivity (de, ee >99%) via base mediated ring opening of aziridines/epoxides with 3-methylindoles followed by BF·OEt catalyzed Pictet-Spengler reaction is accomplished. Interestingly, PTSA promoted cyclization led to the formation of oxidized 3,4-dihydropyrazino[1,2- a]indoles in excellent yields via an unprecedented Pictet-Spengler-detosylation cascade.

Mn /Ag Relay Catalysis: Traceless Diazo-Assisted C(sp )-H/C(sp )-H Coupling to β-(Hetero)Aryl/Alkenyl Ketones.

An unprecedented Mn /Ag -relay-catalyzed C(sp )-H/C(sp )-H coupling of (vinyl)arenes with α-diazoketones is reported, wherein the diazo group was exploited as a traceless auxiliary for control of regioselectivity. Challenging β-(hetero)aryl/alkenyl ketones were obtained through this operationally simple approach. The cascade process merges denitrogenation, carbene rearrangement, C-H activation, and hydroarylation/hydroalkenylation.