As two coexisting and fast-growing research fields in modern synthetic chemistry, the merging of organocatalysis and C–H bond functionalization is well foreseeable, and the joint force along this line has been demonstrated to be a powerful approach in making inert C–H bond functionalization more viable, predictable, and selective. In this review, we provide a comprehensive summary of organocatalysis in inert C–H bond functionalization over the past two decades. The review is arranged by types of inert C–H bonds including alkane C–H, arene C–H, and vinyl C–H as well as those activated benzylic C–H, allylic C–H, and C–H bonds alpha to the heteroatom such as nitrogen and oxygen. In each section, the discussion is classified by the explicit organocatalytic mode involved.

Organocatalysis in Inert C–H Bond Functionalization

Ultrasound-promoted Brønsted acid ionic liquid-catalyzed hydrothiocyanation of activated alkynes under minimal solvent conditions

Recent advancements in dehydrogenative cross coupling reactions for CC bond formation

Cross-dehydrogenative coupling: a sustainable reaction for C–C bond formations

C(sp2)–H/O–H cross-dehydrogenative coupling of quinoxalin-2(1H)-ones with alcohols under visible-light photoredox catalysis

Green method for the synthesis of chromeno[2,3-c]pyrazol-4(1H)-ones through ionic liquid promoted directed annulation of 5-(aryloxy)-1H-pyrazole-4-carbaldehydes in aqueous media.

We report here an efficient and green method for Biginelli condensation reaction of aldehydes, β-ketoesters and urea or thiourea catalyzed by Bronsted acidic ionic liquid [Btto][p-TSA] under solvent-free conditions. Compared to the classical Biginelli reaction conditions, the present method has the advantages of giving good yields, short reaction times, near room temperature conditions and the avoidance of the use of organic solvents and metal catalyst.

https://www.mdpi.com/1420-3049/20/3/3811/pdf

An efficient synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and thiones catalyzed by a novel Brønsted acidic ionic liquid under solvent-free conditions.

Ionic Liquid Promoted Diazenylation of N-Heterocyclic Compounds with Aryltriazenes under Mild Conditions.

Highly Efficient Brønsted Acidic Ionic Liquid Promoted Direct Diazenylation of Pyrazolones with Aryltriazenes under Mild Conditions

The heterocyclic ionic liquid-catalyzed direct oxidative amination of benzylic sp3 C–H bonds via intermolecular sp3 C–N bond formation for the synthesis of N-alkylated azoles under metal-free conditions is reported for the first time. The catalyst 1-butylpyridinium iodide can be recycled and reused with similar efficacies for at least eight cycles.

Bin Wang

Papers

Green method for the synthesis of chromeno[2,3-c]pyrazol-4(1H)-ones through ionic liquid promoted directed annulation of 5-(aryloxy)-1H-pyrazole-4-carbaldehydes in aqueous media.

An efficient synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and thiones catalyzed by a novel Brønsted acidic ionic liquid under solvent-free conditions.

Ionic Liquid Promoted Diazenylation of N-Heterocyclic Compounds with Aryltriazenes under Mild Conditions.

Highly Efficient Brønsted Acidic Ionic Liquid Promoted Direct Diazenylation of Pyrazolones with Aryltriazenes under Mild Conditions

Reusable ionic liquid-catalyzed oxidative coupling of azoles and benzylic compounds via sp3 C–N bond formation under metal-free conditions