Ruthenium(IV)-Alkylidene als Katalysatorvorstufen für direkte Arylierungen von Alkenen mit Chlorarenen und eine Anwendung auf die sequenzielle Katalyse

Regiodivergent C-H and Decarboxylative C-C Alkylation by Ruthenium Catalysis: ortho versus meta Position-Selectivity

Ruthenium(II)biscarboxylate complexes enabled the selective alkylation of C-H and C-C bonds at the ortho- or meta-position. ortho-C-H Alkylations were achieved with 4-, 5- as well as 6-membered halocycloalkanes. Furthermore, the judicious choice of the directing group allowed for a full control of ortho-/meta-selectivities. Detailed mechanistic studies by experiment and computation were performed and provided strong support for an oxidative addition/reductive elimination process for ortho-alkylations, while a homolytic C-X cleavage was operative for the meta-selective transformations.

Directing Group Assisted Unsymmetrical Multiple Functionalization of Arene C-H Bonds

Multiple C-H bond functionalizations promptly install diverse groups on the molecular framework and consequently fabricate complex molecular entities. This review briefly surveys the conceptual development of directing group assisted unsymmetrical multiple functionalization of arene C(sp² )-H bonds, which is exceedingly appealing and highly important.

C-H Oxygenation Reactions Enabled by Dual Catalysis with Electrogenerated Hypervalent Iodine Species and Ruthenium Complexes

The catalytic generation of hypervalent iodine(III) reagents by anodic electrooxidation was orchestrated towards an unprecedented electrocatalytic C-H oxygenation of weakly coordinating aromatic amides and ketones. Thus, catalytic quantities of iodoarenes in concert with catalytic amounts of ruthenium(II) complexes set the stage for versatile C-H activations with ample scope and high functional group tolerance. Detailed mechanistic studies by experiment and computation substantiate the role of the iodoarene as the electrochemically relevant species towards C-H oxygenations with electricity as a sustainable oxidant and molecular hydrogen as the sole by-product. para-Selective C-H oxygenations likewise proved viable in the absence of directing groups.

Ligand Substitution of Ru II –Alkylidenes to Ru(bpy) 3 2+ : Sequential Olefin Metathesis/Photoredox Catalysis

Ruthenium(II) alkylidene complexes such as the Grubbs’ 1st and 2nd generation catalysts undergo a ligand substitution with 2,2′‐bipyridine, which readily leads to the common photoredox catalyst Ru(bpy)₃²⁺. The application of this catalyst transformation in sequential olefin metathesis/photoredox catalysis is demonstrated by way of ring‐closing metathesis (RCM)/photoredox ATRA reactions.

Arene-Free Ruthenium(II/IV)-Catalyzed Bifurcated Arylation for Oxidative C-H/C-H Functionalizations

Experimental and computational studies provide detailed insight into the selectivity- and reactivity-controlling factors in bifurcated ruthenium-catalyzed direct C-H arylations and dehydrogenative C-H/C-H functionalizations. Thorough investigations revealed the importance of arene-ligand-free complexes for the formation of biscyclometalated intermediates within a ruthenium(II/IV/II) mechanistic manifold.

Micellar Catalysis for Ruthenium(II)-Catalyzed C-H Arylation: Weak-Coordination-Enabled C-H Activation in H2 O

Chemoselective C-H arylations were accomplished through micellar catalysis by a versatile single-component ruthenium catalyst. The strategy provided expedient access to C-H-arylated ferrocenes with wide functional-group tolerance and ample scope through weak chelation assistance. The sustainability of the C-H arylation was demonstrated by outstanding atom-economy and recycling studies. Detailed computational studies provided support for a facile C-H activation through thioketone assistance.

Ruthenium(II)-Catalyzed Dearomatized C-H Activation and Annulation Reaction of Vinylnaphthols with Alkynes: Access to Spiro-Pentacyclic Naphthalenones

The ruthenium(II)-catalyzed annulation of vinylnaphthols and alkynes is described. The reaction proceeds through C-H activation, dearomatization, and alkyne insertion. This reaction affords spiro-pentacyclic naphthalenones that have biological significance in good yields.

Triazole-assisted ruthenium-catalyzed C-H arylation of aromatic amides

Site-selective ruthenium(II)-catalyzed direct arylation of amides was achieved through CH cleavages with modular auxiliaries, derived from easily accessible 1,2,3-triazoles. The triazolyldimethylmethyl (TAM) bidentate directing group was prepared in a highly modular fashion through copper(I)-catalyzed 1,3-dipolar cycloaddition and allowed for ruthenium-catalyzed CH arylations on arenes and heteroarenes, as well as alkenes, by using easy-to-handle aryl bromides as the arylating reagents. The triazole-assisted CH activation strategy was found to be widely applicable, to occur under mild reaction conditions, and the catalytic system was tolerant of important electrophilic functionalities. Notably, the flexible triazole-based auxiliary proved to be a more potent directing group for the optimized ruthenium(II)-catalyzed direct arylations, compared with pyridyl-substituted amides or substrates derived from 8-aminoquinoline.

Ruthenium(II)/N-heterocyclic carbene catalyzed [3+2] carbocyclization with aromatic N-H ketimines and internal alkynes

A convenient and highly efficient synthesis of indenamines has been developed via ruthenium-catalyzed [3+2] carbocyclization under very mild conditions. A catalyst system of Ru(II) π-allyl precursor and N-heterocyclic carbene (NHC) ligand promotes facile coupling between aromatic N–H ketimines with internal alkynes at mild temperatures, without added oxidants or other metal salts, and in non-polar solvents. A proposed mechanism involves imine-directed activation of aromatic C–H bond, alkyne insertion, and carbocyclization by intramolecular imine insertion into Ru–alkenyl linkages.

Palladium(II)-Catalyzed Regioselective Ortho Arylation of sp(2) C-H Bonds of N-Aryl-2-amino Pyridine Derivatives

The direct arylation of N-(2-pyridyl) substituted anilines is described. Arylation takes place in ortho position to the amine functionality and is directed by the pyridine N-substituent. Remarkably, N-arylation was never observed as a competing process even though conditions also suitable for Buchwald-Hartwig reactions were applied. The scope of the reaction was investigated in terms of aryl donors as well as the electronic nature of the substrate. Good yields were obtained for most examples through an operationally simple procedure, which did not require inert conditions or even glove box techniques. Pd(OAc)(2) was applied as a cheap catalyst and boronic acids as readily available aryl donors. To obtain full conversion, 1,4-benzoquinone and a silver salt (e.g., Ag(2)O) were required as additives and reacted at relatively mild temperatures (e.g., 80 °C). Additionally, the pyridine-directing group was cleaved after the reaction to give ortho-arylated aniline derivatives.

Transition-metal-catalyzed direct arylation of (hetero)arenes by C-H bond cleavage

The area of transition-metal-catalyzed direct arylation through cleavage of C-H bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional cross-coupling reactions with organometallic reagents. In particular, palladium and ruthenium catalysts have been described that enable the direct arylation of (hetero)arenes with challenging coupling partners--including electrophilic aryl chlorides and tosylates as well as simple arenes in cross-dehydrogenative arylations. Furthermore, less expensive copper, iron, and nickel complexes were recently shown to be effective for economically attractive direct arylations.