Honggen Wang

A Direct Intramolecular C-H Amination Reaction Cocatalyzed by Copper(II) and Iron(III) as Part of an Efficient Route for the Synthesis of Pyrido[1,2-a]benzimidazoles from N-Aryl-2-aminopyridines

A novel and efficient synthesis of pyrido[1,2-a]benzimidazoles through direct intramolecular aromatic C-H amination of N-aryl-2-aminopyridines has been developed. The reaction, cocatalyzed by Cu(OAc)(2) and Fe(NO(3))(3)·9H(2)O, is carried out in DMF under a dioxygen atmosphere. Diversified pyrido[1,2-a]benzimidazoles containing various substitution patterns are obtained in moderate to excellent yields by using this procedure. The results of mechanistic studies suggest that a Cu(III)-catalyzed electrophilic aromatic substitution (S(E)Ar) pathway is operating in this process. The unique role of iron(III) is believed to lie in its ability to facilitate formation of the more electrophilic Cu(III) species. In the absence of iron(III), a much less efficient and reversible Cu(II)-mediated S(E)Ar process takes place.

Mild Rh(III)-Catalyzed C–H Activation and Annulation with Alkyne MIDA Boronates: Short, Efficient Synthesis of Heterocyclic Boronic Acid Derivatives

Taking advantage of Rh(III)-catalyzed C-H activation reactions, we have developed a mild, short, and efficient method for the synthesis of bench-stable 3-isoquinolone MIDA boronates. The reaction is practical and scalable. The product formed has been applied in the Suzuki-Miyaura reaction with high efficiency. This strategy has also been successfully expanded to the synthesis of MIDA boronate functionalized heterocycles such as isoquinoline, pyrrole, and indole.

Mild Rhodium(III)‐Catalyzed CH Activation and Intermolecular Annulation with Allenes

All(enes) great! A novel Rh(III)-catalyzed oxidative coupling with allenes under mild conditions provides heterocycles with exocyclic double bonds. This reaction features low catalyst loadings, high regio- and stereoselectivity, and excellent substrate scope. The products were derivatized and preliminary mechanistic studies were conducted.

Rh[III]-Catalyzed Direct C–H Amination Using N-Chloroamines at Room Temperature

An efficient Rh(III)-catalyzed direct C-H amination of N-pivaloyloxy benzamides with N-chloroamines proceeding at room temperature was achieved. The versatile directing group allows for selective mono- and diamination and can be readily converted to give valuable benzamide or aminoaniline derivatives. Mechanistic studies have been carried out to elucidate the reaction pathway.

Mild Rhodium(III)‐Catalyzed Direct CH Allylation of Arenes with Allyl Carbonates

Owing to the versatility of the allyl group as a handle to access various functional groups, the introduction of an allyl moiety to an aromatic ring allows for rapid buildup of molecular complexity. Besides, allylarene fragment itself is found in a range of natural products and biologically active compounds. Therefore, the synthesis of allylarenes has attracted the attention of synthetic chemists for many years. Crosscoupling reactions based on a prefunctionalized arene have proven to be a powerful method to this purpose (Scheme 1a). Nevertheless, from a stepand atom-economic

Rhodium(III) and Hexabromobenzene—A Catalyst System for the Cross‐Dehydrogenative Coupling of Simple Arenes and Heterocycles with Arenes Bearing Directing Groups

C(6)Br(six) & drugs! C(6)Br(6) can be used as the cooxidant/catalyst modifier for the [Rh(III)Cp*]-catalyzed (Cp*=C(5)Me(5)) dehydrogenative cross-coupling of benzamides with simple benzene derivatives (see scheme, DG=directing group). Similarly, heterocycles can be coupled and druglike structures formed. Mechanistic studies suggest a unique and multiple role of the Cu(OAc)(2)/C(6)Br(6) system and a nonchelate-assisted C-H activation as the rate-determing step.

Palladium-Catalyzed Intramolecular C(sp2)–H Amidination by Isonitrile Insertion Provides Direct Access to 4-Aminoquinazolines from N-Arylamidines

An efficient method for the synthesis of 4-amino-2-aryl(alkyl)quinazolines from readily available N-arylamidines and isonitriles via palladium-catalyzed intramolecular aryl C-H amidination by isonitrile insertion has been developed.

Rh[III]-catalyzed C-H amidation using aroyloxycarbamates to give N-Boc protected arylamines.

The Rh(III)-catalyzed amidation of C(sp(2))-H bonds by the use of electron-deficient aroyloxycarbamates as efficient electrophilic amidation partners is reported. The reaction proceeded under mild conditions with broad functional group tolerance, and pyridine and O-methyl hydroxamic acids serve as efficient directing groups, giving access to valuable N-Boc protected arylamines (also Fmoc and Cbz). Preliminary mechanistic experiments are discussed.

[3]Dendralene Synthesis: Rhodium(III)‐Catalyzed Alkenyl CH Activation and Coupling Reaction with Allenyl Carbinol Carbonate

[3]DendrAl(l)ene! A new synthesis of [3]dendralenes is based on a Rh(III) -catalyzed alkenyl CH activation and coupling reaction with allenyl carbinol carbonates (see scheme; DG=directing group). A variety of [3]dendralenes with diverse substitution patterns are accessible with good efficiency. The reaction is highly stereoselective and compatible with different directing groups and numerous functional groups.

Cp*Co(III)-Catalyzed Annulations of 2-Alkenylphenols with CO: Mild Access to Coumarin Derivatives

Cp*Co(III)-catalyzed annulations of 2-alkenylphenols with CO for the synthesis of coumarin derivatives have been developed. The reaction features mild reaction conditions, broad substrate scope, and good functional group tolerance. Preliminary mechanistic studies were conducted, suggesting that C-H activation is the turnover limiting step. Furthermore, the efficiency of this reaction was demonstrated by the rapid total synthesis of three natural products herniarin, xanthyletin, and seselin.