Ruthenium-catalyzed Oxidative Alkenylation of Arenes via Regioselective C–H Bond Cleavage Directed by a Nitrogen-containing Group

Abstract

Direct alkenylation of 1-phenylpyrazoles with alkenes such as acrylates accompanied by regioselective C–H bond cleavage proceeds efficiently under ruthenium catalysis in the presence of a copper oxidant. The procedure is also applicable to 2-phenylbenzothiazole and benzanilide.

CH Functionalization of Phenols Using Combined Ruthenium and Photoredox Catalysis: In Situ Generation of the Oxidant

“…In the area of material science, the phenol motif plays a crucial role for the construction of poly(phenol ethers) or their modification to adjust their macroscopic properties, such as their melting or glass-transition temperatures, for specific applications. [5] The catalytic system, consisting of [{Ru(p-cymene)Cl 2 } 2 ] (5 mol %) and Cu(OAc) 2 (2 equiv) as the co-oxidant enabled the efficient coupling of the biaryl moiety with common acrylates. [2] Evidently, C À H functionalization plays a more and more important role in method development as disadvantages, such as prefunctionalization with halogens or reactivity problems with lighter halogens, have been overcome.…”

“…The group of Satoh and Miura showed that pyrazole is a suitable directing group (DG) for the ortho olefination of 1-phenylpyrazoles. [5] The catalytic system, consisting of [{Ru(p-cymene)Cl 2 } 2 ] (5 mol %) and Cu(OAc) 2 (2 equiv) as the co-oxidant enabled the efficient coupling of the biaryl moiety with common acrylates. The use of large amounts of copper salts is a general feature of these types of reactions as the in situ generated metal complex needs to be reoxidized first before the next catalytic cycle can be started.…”

Ru‐Catalyzed Branched versus Linear Selective C3‐Alkylation of 2‐Aroylbenzofurans with Acrylates via CH Activation

“…Quite interestingly, the first example on the ruthenium‐catalyzed, cross‐dehydrogenative coupling of alkyl acrylates was reported recently and employed benzo[ b ]furan‐2‐carboxylate derivatives as substrates 11. The scope of this ruthenium‐catalyzed, cross‐dehydrogenative coupling of alkyl acrylates has rapidly expanded to various other aryl/heteroaryl systems by using directing groups other than carboxylate 4h–o. Despite the widespread application in dehydrogenative couplings, surprisingly, a Ru‐catalyzed alkylation with acrylates via CH activation has not yet been documented 12.…”

“…Initial exploratory experiments were carried out by using benzo[ b ]furan 1 a as the substrate and methyl acrylate 2 a as an acceptor (Table 1). In general, the cationic ruthenium complexes in combination with an oxidant, have been used for the alkenylations 4h–o. In anticipation of the requisite alkylation, various neutral ruthenium complexes have been explored in this pursuit by using adamantane‐1‐carboxylic acid (AdCO 2 H) as an additive.…”

Unprecedented Transformation of a Directing Group Generated In Situ and Its Application in the One‐Pot Synthesis of 2‐Alkenyl Benzonitriles

“…In recent years, the functionalisation of unreactive ortho arene CH bonds1 through transition‐metal‐catalysed directing‐group (DG) assisted strategies2 has been the subject of a number of intense investigations. Although numerous DGs comprising carboxylic,3a–d ester,3e carbonyl,3f–g sulfoximine,3h–i phosphinoxy,3j nitroso,3k ether,3l and heterocycle3m–o derivatives have been employed for regioselective arene CH olefination, reports involving the generation of a DG in situ and its transformation are scarce 4…”