Ruthenium Oxidase Catalysis for Site‐Selective C–H Alkenylations with Ambient O₂ as the Sole Oxidant

Abstract

Ruthenium(II) oxidase catalysis by direct dioxygen-coupled turnover enabled step-economical oxidative C-H alkenylation reactions at ambient pressure. Versatile ruthenium(II) biscarboxylate catalysts displayed ample substrate scope and proved applicable to weakly coordinating and removable directing groups. The twofold C-H functionalization strategy was characterized by exceedingly mild reaction conditions as well as excellent positional selectivity.

Cascade One‐Pot Synthesis of Orange‐Red‐Fluorescent Polycyclic Cinnolino[2,3‐f]phenanthridin‐9‐ium Salts by Palladium(II)‐Catalyzed C−H Bond Activation of 2‐Azobiaryl Compounds and Alkenes

“…On the basis of previous TM-catalyzed directing-groupassisted C À Hb ond olefination/annulation reactions, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] we propose the following mechanism for the present reaction (Scheme 4a): First, the catalytic cycle is most likely initiated by coordination of the diazo group to ap alladium species, followed by ortho CÀHa ctivation to form as ix-membered palladacycle D1. [a] Unless otherwise mentioned, reactions were carried out using a2azobiaryl 2 (0.10 mmol), an alkene 3 (0.20 mmol), Pd(OAc) 2 (10 mol %), Cu(OAc) 2 (0.30 mmol), CuCl 2 ·(0.30 mmol), and TFE (2.0 mL) at 110 8 8C for 16 h. Yields are for the isolated product.…”

“…[2] Azobenzenes are an important class of compounds as food additives,d yes,i ndicators, photochemical switches,and pharmaceuticals. [3] Thesynthesis of polycyclic N-heterocycles by C À Ha ctivation of azobenzenes and substrates with other directing groups (DGs) and treatment with alkenes is known for various transition metals (TMs), such as rhodium, [4] ruthenium, [5] cobalt, [6] and nickel. [7] In the last decade,p alladium-catalyzed direct C(sp 2 )ÀHa nd C(sp 3 )ÀHalkenylation reactions of arenes with alkenes have been reported.…”

Enhancing Ru(II)‐Catalysis with Visible‐Light‐Mediated Dye‐Sensitized TiO2 Photocatalysis for Oxidative C−H Olefination of Arene Carboxylic Acids at Room Temperature

“…To this end, we attempted to delve into the consonance of other coupling partners under the current conditions. Delightfully, ethyl acrylate was also well‐suited under the catalytic conditions, furnishing 3 s – u in good yields (Scheme ) . The protocol was also competent to perform an oxidative annulation between benzoic acid and alkyne at room temperature to produce isocoumarin 5 in 76 % yield (Scheme ) …”

Ruthenium(II)biscarboxylate‐Catalyzed Hydrogen‐Isotope Exchange by Alkene C−H Activation

“…The practical utility and key mechanistic implications of the C−H activation‐based HIE was next applied to the position‐ and chemo‐selective preparation of biorelevant, naturally occurring compounds. Hence, our HIE approach proved applicable towards the preparation of phthalides of type [D] 3 ‐ 5 b (Scheme a) – key structural motifs in various natural products – from substrate [D 2 ]‐ 4 without notable primary kinetic isotope effect (KIE) in the ruthenium oxidase, catalysis manifold (Scheme b).…”