Qinghe Gao

I2-Catalyzed Oxidative Cross-Coupling of Methyl Ketones and Benzamidines Hydrochloride: A Facile Access to α-Ketoimides

An iodine-catalyzed oxidative cross-coupling of C-H/N-H has been demonstrated. This simple and efficient approach constructed α-ketoimides in good to excellent yields from methyl ketones and benzamidines hydrochloride under metal-free and peroxide-free conditions. This synthetic strategy was achieved via an in situ iodination-based oxidative coupling pathway.

Metal-Free sp3 C—H Bond Dual-(Het)arylation: I2-Promoted Domino Process to Construct 2,2-Bisindolyl-1-arylethanones.

A molecular I(2)-promoted sp(3) C-H bond dual-(het)arylation protocol was developed for the synthesis of 2,2-bisindolyl-1-arylethanones. Through a logical design, three mechanism-different reactions (iodination, Kornblum oxidation, and Friedel-Crafts reaction) were assembled in a single reactor. A variety of 2,2-bisindolyl-1-aryl ethanones were synthesized from simple and readily available aryl methyl ketones and indoles. In the reaction, metal, base, and ligand were all avoidable.

I2-Promoted Selective Oxidative Cross-Coupling/Annulation of 2-Naphthols with Methyl Ketones: A Strategy To Build Naphtho[2,1-b]furan-1(2H)-ones with a Quaternary Center

A highly efficient and selective molecular iodine-promoted oxidative cross-coupling/annulation between 2-naphthols and methyl ketones has been realized. The reaction successfully constructed a new quaternary carbon center within 3(2H)-furanones. Our synthetic strategy provided an in situ iodination-based oxidative coupling pathway. Based on the experimental results, a self-sequenced iodination/Kornblum oxidation/Friedel-Crafts/oxidation/cyclization mechanism was proposed.

Povarov-Type Reaction Using Methyl as New Input: Direct Synthesis of Substituted Quinolines by I2-Mediated Formal [3 + 2 + 1] Cycloaddition

A highly efficient molecular iodine mediated formal [3 + 2 + 1] cycloaddition reaction for the direct synthesis of substituted quinolines from methyl ketones, arylamines, and styrenes is developed. The methyl group of the methyl ketone represents uniquely reactive input in the Povarov reaction. A self-sequenced iodination/Kornblum oxidation/Povarov/aromatization mechanism has been proposed as a possible reaction sequence to account for the results observed in this study.

Direct Regioselective Oxidative Cross-Coupling of Indoles with Methyl Ketones: A Novel Route to C3-Dicarbonylation of Indoles

The first C3-dicarbonylation of indoles was realized through direct oxidative cross-coupling of indoles with methyl ketones in the presence of molecular iodine and pyrrolidine. This reaction constructed a highly efficient indolyl diketones scaffold, which might be regarded as a useful biological and pharmacological tool in the exploration of therapeutic A2BAR modulators. The use of inexpensive molecular iodine and pyrrolidine and a broad substrate scope make this protocol very practical. Preliminary mechanistic studies indicate that two paths are involved in this process.

Direct Annulation of Hydrazides to 1,3,4-Oxadiazoles via Oxidative C(CO)–C(Methyl) Bond Cleavage of Methyl Ketones

A new strategy for the synthesis of 1,3,4-oxadiazoles was established through direct annulation of hydrazides with methyl ketones. It was found that the use of K2CO3 as a base achieves an unexpected and highly efficient C-C bond cleavage. This reaction is proposed to go through oxidative cleavage of Csp(3)-H bonds, followed by cyclization and deacylation.

Unexpected C–C Bond Cleavage: A Route to 3,6-Diarylpyridazines and 6-Arylpyridazin-3-ones from 1,3-Dicarbonyl Compounds and Methyl Ketones

An unexpected C-C bond cleavage has been revealed in the absence of metal. This observation has been exploited to develop an efficient approach toward 3,6-diarylpyridazines and 6-arylpyridazin-3-ones from simple and commercially available 1,3-dicarbonyl compounds and methyl ketones.

Design and Synthesis of 2‑Acylbenzothiazoles via In Situ Cross- Trapping Strategy from Benzothiazoles with Aryl Ketones

An I2/KOH synergistically promoted direct ring-opening aroylation of benzothiazoles with aryl ketones has been discovered. Aryl ketones were seen to act as carbonyl sources to construct 2-acylbenzothiazoles. This reaction could provide an example for the convergent integration of self-labor domino sequences based on an in situ cross-trapping strategy.

Dual Roles of Methyl Ketones in Radziszewski-Type Reaction: Formal [2 + 1 + 1 + 1] Synthesis of 1,2,5-Trisubstituted Imidazoles

A highly efficient molecular iodine mediated Radziszewski-type reaction of methyl ketones, anilines, and tosylmethyl isocyanide has been developed. This protocol represents an elegant molecular fragment assembly of imidazoles via a formal [2 + 1 + 1 + 1] annulation. It is the first example where methyl ketones serve as the α-dicarbonyl compounds and aldehydes in Radziszewski-type reactions.

Iodine-Promoted Oxidative Cross-Coupling of Unprotected Anilines with Methyl Ketones: A Site-Selective Direct C-H Bond Functionalization to C4-Dicarbonylation of Anilines.

An unprecedented direct dual C-H bond functionalization of unprotected anilines and methyl ketones has been demonstrated. It is the first example of iodine-promoted highly chemo- and site-selective oxidative C-H/C-H cross-coupling of anilines and methyl ketones to furnish the C4-dicarbonylation of anilines in moderate to good yields. Moreover, coproduct HI acted as a catalyst in the reaction. The salient feature of this approach is unprecedented C-H functionalization rather than N-H functionalization of unprotected anilines.