Unactivated Arenes Research Articles

ChemInform Abstract: Nickel‐Catalyzed and Benzoic Acid‐Promoted Direct Sulfenylation of Unactivated Arenes.

AbstractDepending on substitution pattern, N‐(2‐(pyridin‐2‐yl)propan‐2‐yl)arylamides are regioselectively mono‐ and/or bis‐arylsulfenylated with diaryl disulfides (II) and (IX) in the ortho‐position(s) next to the amide group.

Palladium-catalyzed regioselective decarboxylative alkylation of arenes and heteroarenes with aliphatic carboxylic acids.

An unprecedented Pd(OAc)2-catalyzed decarboxylative alkylation of unactivated arenes, with aliphatic carboxylic acids as inexpensive alkyl sources, is reported. The alkylation, controlled by the directing group, is regioselective, shows high functional group tolerance, and provides mild access to alkylated indolines, 2-phenylpyridines, and azobenzenes under solvent-free conditions in moderate to high yields.

Cobalt(III)‐Catalyzed Aryl and Alkenyl CH Aminocarbonylation with Isocyanates and Acyl Azides

Expedient C-H aminocarbonylations of unactivated (hetero)arenes and alkenes were accomplished with a cobalt(III) catalyst that shows high functional group tolerance. The C-H functionalization occurred with excellent chemo-, site-, and diastereoselectivity and enabled step-economical reactions with isocyanates or acyl azides.

Photoinduced C-H direct arylation of unactivated arenes

Two general protocols have been developed for the photoinduced, metal-free direct arylation of unactivated arenes with aryl iodide. Both methods gave good to excellent yields for most substrates. Notably, the C-F bond in method A and the C-F, C-Cl, and C-Br bonds in method B could survive the arylation reaction. These methods offered excellent options for syntheses of biaryls.

ChemInform Abstract: A Direct C—H Arylation of Unactivated Arenes Promoted by Mixed Potassium Alkoxides.

AbstractThe use of mixed alkoxides as base is the key to success for the direct arylation of benzene with aryl iodides.

Potassium ethoxide/phenanthroline promoted chemoselective direct C–H arylation of unactivated arenes with aryl iodides

Simple and cheap potassium ethoxide (EtOK) and a catalytic amount of phenanthroline can efficiently promote the direct C–H arylation of unactivated arenes with aryl iodides at 80 °C. This transition-metal-free base-promoted homolytic aromatic substitution offers a chemoselective approach to synthesize biaryls bearing active halo substituents (I, Br, Cl, etc.) in good yields.

ChemInform Abstract: Iron‐Mediated Direct Arylation of Unactivated Arenes in Air.

AbstractIt is demonstrated that a preformed Fe/phen complex catalyzes the direct C‐H arylation with aryl iodides and bromides using excess KOtBu as the base without the use of an inert atmosphere and/or forcing conditions.

ChemInform Abstract: Direct Intermolecular C—H Arylation of Unactivated Arenes with Aryl Bromides Catalyzed by 2‐Pyridyl Carbinol.

ChemInform Abstract: Direct Intermolecular C—H Arylation of Unactivated Arenes with Aryl Bromides Catalyzed by 2‐Pyridyl Carbinol.

ChemInform Abstract: p‐Toluenesulfonohydrazide as Highly Efficient Initiator for Direct C—H Arylation of Unactivated Arenes.

AbstractA highly efficient and relatively mild direct arylation of unactivated arenes with aryl iodides, bromides, or chlorides without the need of any transition metal is presented.

Transition-metal-free synthesis of phenanthridinones from biaryl-2-oxamic acid under radical conditions.

Na2S2O8-promoted decarboxylative cyclization of biaryl-2-oxamic acid for phenanthridinones has been developed. This work illustrates the first example of intramolecular decarboxylative amidation of unactivated arene under transition-metal-free conditions. Additionally, this approach provides an efficient and economical method to access biologically interesting phenanthridinones, an important structure motif in many natural products.

Nickel-catalyzed and benzoic acid-promoted direct sulfenylation of unactivated arenes.

A nickel-catalyzed and benzoic acid-promoted direct sulfenylation of unactivated arenes using removable 2-(pyridine-2-yl)-isopropylamine as a directing group is described. This strategy provides an efficient access to valuable aryl sulfides with ample substrate scope and a high degree of functional group tolerance.

Visible-light-driven difluoroacetamidation of unactive arenes and heteroarenes by direct C-H functionalization at room temperature.

The directed difluoroacetamidation of unactivated arenes and heteroarenes with bromodifluoroacetamides via visible-light photoredox catalysis has been efficiently achieved at room temperature. Broad utility of this transformation is presented, including electronically deficient heteroaromatic and aromatic systems. The mechanistic pathway of the difluoroacetamidation was discussed based on photoluminescence quenching, spin-trapping, and kinetic isotope effect experiments.

ChemInform Abstract: Hydroarylation of Arynes Catalyzed by Silver for Biaryl Synthesis.

AbstractA new biaryl synthesis via silver‐catalyzed intra‐ and intermolecular hydroarylation of acyclic arynes with unactivated arenes is developed.

A Direct CH Arylation of Unactivated Arenes Promoted by Mixed Potassium Alkoxides

AbstractAn intermolecular CH arylation of unactivated arenes with aryl iodides is made viable through a transition‐metal‐free approach. This simple and efficient process obviates the common use of diamines or diols as the promoters. With the aid of only mixed potassium alkoxides, a number of unactivated arene CH bonds can be directly arylated through a homolytic aromatic substitution (HAS) pathway.

P-Toluenesulfonohydrazide as highly efficient initiator for direct C-H arylation of unactivated arenes.

p-Toluenesulfonohydrazide (PTSH) was shown to promote the highly efficient direct arylation of unactivated arenes with aryl iodides, bromides, or chlorides in the presence of potassium tert-butoxide without the assistance of any transition metals. The reaction proceeds through base-promoted homolytic aromatic substitution (BHAS) involving aryl radicals and arylradical anions as intermediates.

ChemInform Abstract: Palladium‐Catalyzed Oxidative C—H/C—H Cross‐Couplings of Thiazolo[5,4‐d]pyrimidine with Aromatic (Hetero)cycles.

Abstract A novel Pd(II)-catalyzed dehydrogenative cross-coupling reaction of thiazolo[5,4- d ]pyrimidine with unactivated (hetero)arenes via C–H bond activation was achieved. This protocol provides a straightforward and operationally simple method for the synthesis of 2-arylsubstituted thiazolo[5,4- d ]pyrimidines of interest in pharmaceutical sciences.

Fluoro and Trifluoromethyl Derivatives of POCOP-Type Pincer Complexes of Nickel: Preparation and Reactivities in SN2 Fluorination and Direct Benzylation of Unactivated Arenes

This report describes the synthesis, characterization, and reactivities of the pincer-type complexes κP,κC,κP-(R-POCOP)NiX (R-POCOP = 2,6-(i-Pr2PO)2,4-R-C6H3; R = H, X = F (2a), CF3 (3a); R = OMe, X = F (2b), X = CF3 (3b)). These complexes were prepared by treating their Ni–Br analogues with excess AgF at rt (2a and 2b) or excess AgF and Me3SiCF3 (3a and 3b) at 45 °C. The Ni–F derivative 2a was shown to be an intermediate for the formation of the Ni–CF3 derivative 3a. Complexes 2a, 3a, and 3b were fully characterized by multinuclear NMR spectroscopy, cyclic voltammetry, and X-ray diffraction analysis. Variable temperature, multinuclear NMR analysis of 2a helped elucidate interaction of the fluoride ligand with hydrofluoric acid present in the reaction medium. The bromo complexes 1a or 1b catalyzed fluorination of benzyl halides at 90 °C in the presence of excess AgF, whereas the Ni–CF3 complexes 3 failed to promote trifluoromethylation of benzyl bromide, leading instead to a direct benzylation of the aromatic reaction solvent (benzene, toluene, xylene, or bromobenzene). Possible mechanisms for this benzylation reaction have been probed and discussed.

ChemInform Abstract: Rhodium‐Catalyzed Intermolecular C—H Silylation of Arenes with High Steric Regiocontrol.

Regioselective C–H functionalization of arenes has widespread applications in synthetic chemistry. The regioselectivity of these reactions is often controlled by directing groups or steric hindrance ortho to a potential reaction site. Here, we report a catalytic intermolecular C–H silylation of unactivated arenes that manifests very high regioselectivity through steric effects of substituents meta to a potential site of reactivity. The silyl moiety can be further functionalized under mild conditions but is also inert toward many common organic transformations, rendering the silylarene products useful building blocks. The remote steric effect that we observe results from the steric properties of both the rhodium catalyst and the silane.

ChemInform Abstract: Di‐tert‐butyl Peroxide Promoted Direct C—H Arylation of Unactivated Arenes with Aryl Halides.

ChemInform Abstract: Di‐tert‐butyl Peroxide Promoted Direct C—H Arylation of Unactivated Arenes with Aryl Halides.

ChemInform Abstract: Direct C—H Arylations of Unactivated Arenes Catalyzed by Amido‐Functionalized Imidazolium Salts.

AbstractAn effective organocatalytic system based on an amido‐functionalized imidazolium salt allows the synthesis of biaryls from arylhalides and benzene.