Cyclic ethers to esters and monoesters to bis-esters with unconventional coupling partners under metal free conditions via sp3 C–H functionalisation

Oxidative esterification of sp³ C–H bonds in simple solvents has been achieved using latent ArCOO⁻ sources under metal free conditions.

Versatile palladium-catalyzed C–H olefination of (hetero)arenes at room temperature

The room-temperature oxidative C–H/C–H cross-couplings between simple arenes and alkenes, coumarins or quinones have been reported by using a highly electrophilic palladium species [Pd(TFA)₂] as the catalyst and cheap (NH₄)₂S₂O₈ as the oxidant under air.

Controllable mono-/di-alkenylation of aryl alkyl thioethers tuned by oxidants via Pd-catalysis

Oxidant controlled selective C–H bond mono-alkenylation and di-alkenylation of biphenylthioethers to synthesize sulfoxide-olefin ligands with thioether as the directing group.

Synthesis of alkylidene pyrrolo[3,4-b]pyridin-7-one derivatives via RhIII-catalyzed cascade oxidative alkenylation/annulation of picolinamides

A practical Rh-catalyzed oxidative cascade ortho-olefination/annulation of picolinamides leading to pyrrolo[3,4-b]pyridines has been developed.

Rh(iii)-catalyzed regioselective hydroarylation of alkynes via directed C–H functionalization of pyridines

Rh(iii)-catalyzed C-3 selective alkenylation of pyridines via hydroarylation of alkynes has been developed. The reaction shows high regioselectivity, high yield and good functional group tolerance, providing a convenient strategy for the synthesis of trisubstituted alkenes.

Rh(iii)-catalyzed tandem oxidative olefination-cyclization of aryl sulfonamides

An efficient Rh(iii)-catalyzed ortho-selective C–H activation and tandem oxidative olefination-cyclization of aryl sulfonamides is described. The protocol has been applied to various substrates with good functional group tolerance.

Rhodium(iii)-catalyzed regioselective C2-amidation of indoles with N-(2,4,6-trichlorobenzoyloxy)amides and its synthetic application to the development of a novel potential PPARγ modulator

Here an efficient rhodium(iii)-catalyzed C2-amidation of indoles and its synthetic application to a new PPARγ modulator have been developed.

Ruthenium-catalyzed double-fold C–H tertiary alkoxycarbonylation of arenes using di-tert-butyl dicarbonate

An efficient ruthenium-catalyzed double-fold C–H bond alkoxycarbonylation of arenes was developed using commercially available Boc₂O as the tertiary esterification reagent.

sp3C–H bond alkylation of ketones with alkenes via ruthenium(ii) catalysed dehydrogenation of alcohols

The sp³C–H bond alkylation of 2-pyridylethanols upon reaction with alkenes, with a [RuCl₂(arene)]₂ catalyst and Cu(OAc)₂·H₂O proceeds via a tandem dehydrogenation/alkylation with alkenes of the resulting ketone.

Ruthenium-catalyzed alkenylation of azoxybenzenes with alkenes through ortho-selective C–H activation

A highly selective alkenylation of azoxybenzenes catalyzed by the Ru^III-complex was developed, providing olefinated azoxy compounds in good yields.

Selective approach to thioesters and thioethers via sp3 C–H activation of methylarenes

Novel CDC approaches for the synthesis of thioesters and thioethers was developed via sp³ C–H activation of methylarenes and subsequent functionalization.

Direct functionalization of unactivated C-H bonds catalyzed by group 3-5 metal alkyl complexes

This perspective summarizes direct C-H bond functionalization reactions catalyzed by group 3-5 metal alkyl complexes. Metal-carbon bonds of group 3-5 metals have potentially high reactivity toward both C-H bond activation reactions through the intrinsic σ-bond metathesis pathway and insertion of unsaturated organic molecules. Upon the combination of these two elemental steps, direct C-H bond functionalization reactions of (hetero)aromatic compounds, methane, alkylamines, and terminal alkynes, proceed through C(sp)-H, C(sp(2))-H, and C(sp(3))-H bond activation reactions. Here we review as catalysts for these transformations not only simple metallocene complexes but also non-metallocene complexes supported by a variety of ligands, which are often superior in terms of catalyst design and catalytic activity.

Rhodium-catalyzed annulative coupling of 3-phenylthiophenes with alkynes involving double C-H bond cleavages

Double CH bond activation took place efficiently upon treatment of 3-phenylthiophenes with alkynes in the presence of a rhodium catalyst and a copper salt oxidant to form the corresponding naphthothiophene derivatives. Dehydrogenative coupling with alkenes was also found to occur on the phenyl moiety rather than the thiophene ring. These reactions provide straightforward synthetic methods for π-conjugated molecules involving a thiophene unit from readily available, simple building blocks.

The cross-dehydrogenative coupling of C(sp3)-H bonds: a versatile strategy for C-C bond formations

Over the last decade, substantial research has led to the introduction of an impressive number of efficient procedures which allow the selective construction of CC bonds by directly connecting two different CH bonds under oxidative conditions. Common to these methodologies is the generation of the reactive intermediates in situ by activation of both CH bonds. This strategy was introduced by the group of Li as cross-dehydrogenative coupling (CDC) and discloses waste-minimized synthetic alternatives to classic coupling procedures which rely on the use of prefunctionalized starting materials. This Review highlights the recent progress in the field of cross-dehydrogenative C sp 3C formations and provides a comprehensive overview on existing procedures and employed methodologies.

Synthesis of isoquinolines via Rh(III)-catalyzed C-H activation using hydrazone as a new oxidizing directing group

An efficient and mechanistically interesting method for the synthesis of highly substituted isoquinolines by a Rh(III)-catalyzed hydrazone directed ortho C-H bond activation and annulation without an external oxidant is described. This reaction is accomplished via a C-C and C-N bond formation along with N-N bond cleavage.

Catalytic functionalization of C(sp2)-H and C(sp3)-H bonds by using bidentate directing groups

C-H bonds are ubiquitous in organic compounds. It would, therefore, appear that direct functionalization of substrates by activation of C-H bonds would eliminate the multiple steps and limitations associated with the preparation of functionalized starting materials. Regioselectivity is an important issue because organic molecules can contain a wide variety of C-H bonds. The use of a directing group can largely overcome the issue of regiocontrol by allowing the catalyst to come into proximity with the targeted C-H bonds. A wide variety of functional groups have been evaluated for use as directing groups in the transformation of C-H bonds. In 2005, Daugulis reported the arylation of unactivated C(sp(3))-H bonds by using 8-aminoquinoline and picolinamide as bidentate directing groups, with Pd(OAc)2 as the catalyst. Encouraged by these promising results, a number of transformations of C-H bonds have since been developed by using systems based on bidentate directing groups. In this Review, recent advances in this area are discussed.

Transition metal-catalyzed C(vinyl)-C(vinyl) bond formation via double C(vinyl)-H bond activation

Transition metal-catalyzed oxidative dehydrogenative coupling reactions of Caryl-H bonds with Cvinyl-H bonds to generate a Caryl-Cvinyl bonds have been well developed in recent decades. However, only a few studies have focused on the direct Cvinyl-Cvinyl bond formation via double Cvinyl-H bond activation. Recent developments in this active area have been highlighted in this tutorial review.

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

A Fe(acac)₃-catalyzed decarboxylative coupling of 2-(aryl)vinyl carboxylic acids with cycloalkanes was developed by using DTBP as an oxidant through a radical process. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields (71–95%). The reaction also shows excellent stereoselectivity, and only trans-isomers are obtained.

Carboxylate assistance for catalyzed hydroarylations of methylenecyclopropanes

Carboxylate assistance enabled efficient and chemoselective ruthenium(II)-catalyzed hydroarylations and hydroalkenylations of highly strained methylenecyclopropanes via C-H bond activation occurring with ring conservation of the cyclopropane moieties.