ABSTRACT
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. A novel S-difunctionalization pathway was discovered using vinyliodonium salts, which proceeds under additive-free reaction conditions and grants excellent stereoselectivity in the synthesis of aryl(vinyl) sulfides. A one-pot strategy combining transition-metal-free diarylation and subsequent reduction provided facile access to electron-rich thioanilines and a direct synthesis of a potential drug candidate derivative. The retained iodo group allows a wide array of further synthetic transformations. Mechanistic insights were elucidated by isolating the key intermediate, and the relevant energy profile was substantiated by DFT calculations.
ABSTRACT
Herein, we report a Cp*IrIII -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 IrIII -allyl species support an intermolecular allylic C-H activation followed by an electrophilic alkynylation.
ABSTRACT
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*RhCl2 ]2 -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. Mechanistic investigations suggest an intermediate RhIII -allyl species is trapped by an electrophilic amidation reagent in a redox-neutral fashion.
ABSTRACT
Herein we describe an unprecedented RuII-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.
ABSTRACT
Herein, we report the redox-neutral, intermolecular, and highly branch-selective amidation of allylic C-H bonds enabled by Cp*IrIII 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 IrIII -allyl intermediate rather than the direct insertion of an Ir-nitrenoid species into the allylic C-H bond.
ABSTRACT
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 BF3·OEt2 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.
ABSTRACT
An unprecedented MnI /AgI -relay-catalyzed C(sp2 )-H/C(sp3 )-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 ß-(hetero)aryl/alkenyl ketones were obtained through this operationally simple approach. The cascade process merges denitrogenation, carbene rearrangement, C-H activation, and hydroarylation/hydroalkenylation. The robustness of this method was demonstrated at preparative scale and applied to late-stage diversification of natural products.
