Nickel-Catalyzed Oxidative Decarboxylative Annulation for the Synthesis of Heterocycle-Containing Phenanthridinones

Cu(II)-Catalyzed Decarboxylative (4 + 2) Annulation of Coumarin-3-Carboxylic Acids with In Situ Generated α,β-Unsaturated Carbonyl Compounds from tert-Propargylic Alcohols

Cu(II)-catalyzed decarboxylative oxidative (4 + 2) annulation of coumarin-3-carboxylic acids with tert-propargylic alcohols, via the in situ generated α,β-unsaturated carbonyl compounds by the Meyer-Schuster rearrangement, has been developed. This protocol involving indirect C-H functionalization offers access to diverse naphthochromenone architectures with good to excellent yields.

Combined Experimental and Computational Mechanistic Investigation of the Palladium-Catalyzed Decarboxylative Cross-Coupling of Sodium Benzoates with Chloroarenes

Reported herein is a mechanistic investigation into the palladium-catalyzed decarboxylative cross-coupling of sodium benzoates and chloroarenes. The reaction was found to be first-order in Pd. A minimal substituent effect was observed with respect to chloroarene, and the reaction was zero-order with respect to chloroarene. Palladium-mediated decarboxylation was assigned as the turnover-limiting step based on an Eyring plot and density functional theory computations. Catalyst performance was found to vary based on the electrophile, which is best explained by catalyst decomposition at Pd(0). The 1,5-cyclooctadiene (COD) ligand contained in the precatalyst CODPd(CH₂TMS)₂ (Pd1) was shown to be a beneficial additive. The bench-stable Buchwald complex XPhosPdG2 could be used with exogenous COD and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (XPhos) instead of complex Pd1. Adding exogenous XPhos significantly increased the catalyst turnover number and enhanced reproducibility.

Organocatalyst in Direct C(sp2)-H Arylation of Unactivated Arenes: [1-(2-Hydroxyethyl)-piperazine]-Catalyzed Inter-/Intra-molecular C-H Bond Activation

This article describes the identification of 1-(2-hydroxyethyl)-piperazine as a new, cost-effective, highly efficient organocatalyst, which promotes both inter- and intra-molecular direct C(_sp²)-H arylations of unactivated arenes in the presence of potassium tert-butoxide. While the inter-molecular C-H arylation of unactivated benzenes with aryl halides (Ar-X; X = I, Br, Cl) toward biaryl syntheses underwent smoothly in the presence of only 10 mol % organocatalyst, the intra-molecular C-H arylation catalytic system composed of 40 mol % each of the catalyst and the additive (4-dimethylaminopyridine (DMAP)). The novel catalyst was also able to perform both inter- and intra-molecular direct arylations simultaneously in a single pot. The mechanistic studies confirmed the involvement of aryl radical anions and proceeded via a single-electron-transfer (SET) mechanism. The large substrate scope, high functional group tolerance, competition experiments, gram-scale synthesis, and kinetic studies further highlight the importance and versatile nature of the methodology as well as the compatibility of the new catalyst. To the best of our knowledge, this is the first report on any organocatalyst that reported detailed investigations of both inter- and intra-molecular direct C(_sp²)-H arylations of unactivated arenes in a single representation.

Selective Quadruple C(sp3)-F Functionalization of Polyfluoroalkyl Ketones

The significance of organofluorine compounds has inspired the establishment of numerous methods for the functionalization of rather inert C-F bonds. Despite advances achieved in the manipulation of C(sp²)-F bonds by employing transition-metal catalysts, such as Pd, Rh, Cu, Ni, Ru, and Ir, strategies that address the paucity of effective pathways for selective activation of multiple C(sp³)-F bonds remained challenging. In this context, we present an unprecedented coupling-aromatization-cyclization reaction of polyfluorinated ketones with diverse N- and S-nucleophiles that forms regiodefined perfluoroalkylated naphtho[1,2-b]furan/benzofuran derivatives by harnessing Co-promoted distinctive quadruple C(sp³)-F bonds cleavage relay. This chemistry involving controlled and successive selective defluorination at heteronuclear centers would greatly contribute to the preparation of drug-like heterocycles as well as the late-stage elaboration of biorelevant compounds. Controlled experiments and DFT theoretical studies revealed that the combination of cheap cobalt salt with Cs₂CO₃ enable expeditious C-F functionalization.

•

First example of consecutive selective quadruple C(sp³)-F functionalization

•

Selectively and controllably partial defluorination at heteronuclear sites

•

Conversion to value-added chemicals by using polyfluorocarbons and nucleophiles

•

DFT calculations were performed to support mechanistic proposal

Bidentate Directing Groups: An Efficient Tool in C-H Bond Functionalization Chemistry for the Expedient Construction of C-C Bonds

During the past decades, synthetic organic chemistry discovered that directing group assisted C-H activation is a key tool for the expedient and siteselective construction of C-C bonds. Among the various directing group strategies, bidentate directing groups are now recognized as one of the most efficient devices for the selective functionalization of certain positions due to fact that its metal center permits fine, tunable, and reversible coordination. The family of bidentate directing groups permit various types of assistance to be achieved, such as N,N-dentate, N,O-dentate, and N,S-dentate auxiliaries, which are categorized based on the coordination site. In this review, we broadly discuss various C-H bond functionalization reactions for the formation of C-C bonds with the aid of bidentate directing groups.

The decarboxylative C–H heteroarylation of azoles catalysed by nickel catalysts to access unsymmetrical biheteroaryls

The direct decarboxylative C–H heteroarylation of azoles with heteroaryl carboxylic acids through nickel catalysts has been developed.