Direct access to isoindolines through tandem Rh(III)-catalyzed alkenylation and cyclization of N-benzyltriflamides

Ru(II)-Catalyzed C-H Alkylation of N-Benzyltriflamide with Maleimides: Synthesis of o-Succinimide Substituted Benzaldehydes

A ruthenium-catalyzed N-benzyltriflamide assisted C-H alkylation with maleimide followed by hydrolysis of in situ generated imine has been developed for the first time. This synthetic method results in the efficient synthesis of o-succinimide derivatives of benzaldehydes. This reaction involves less expensive and mild reaction conditions and shows excellent site selectivity and good functional group compatibility.

Density Functional Theory Study on the Mechanism of Iridium-Catalyzed Benzylamine ortho C-H Alkenylation with Ethyl Acrylate

Iridium-catalyzed oxidative o-alkenylation of benzylamines with acrylates was enabled by the directing group pentafluorobenzoyl (PFB). Density functional theory calculations were performed to explore the detailed reaction mechanism. The calculated results reveal that N-deprotonation prior to C-H activation is favored over direct C-H activation. Moreover, C-H activation is reversible and not the rate-determining step, which has been supported by the experimental observation. The regio- and stereoselectivity of ethyl acrylate insertion are controlled by the steric effect and the carbon atom with a larger orbital coefficient of the π* antibonding orbital in the nucleophilic attack, respectively. The migratory insertion of ethyl acrylate is computationally found to be rate-determining for the whole catalytic cycle. Finally, the seven-membered ring intermediate IM11 undergoes a sequential N-protonation and β-H elimination with the assistance of AcOH, rather than β-H elimination and reductive elimination proposed experimentally, to afford the o-alkenylated product. IM11 is unable to directly cyclize through C-N reductive elimination because both sp³-hybridized N and C atoms are unfavorable for N-C reductive elimination. The origin of the directing group PFB preventing the product and intermediates undergoing aza-Michael addition has been explained.

Rhodium catalyzed template-assisted distal para-C-H olefination

Rhodium catalysis has been extensively used for ortho-C-H functionalization reactions, and successfully extended to meta-C-H functionalization. Its application to para-C-H activation remains an unmet challenge. Herein we disclose the first example of such a reaction, with the Rh-catalyzed para-C-H olefination of arenes. The use of a Si-linked cyanobiphenyl unit as a traceless directing group leads to highly para-selective arene-olefin couplings.

Iridium-Catalyzed Benzylamine C-H Alkenylation Enabled by Pentafluorobenzoyl as the Directing Group

The first iridium-catalyzed oxidative alkeynylation of benzylamines with acrylates enabled by a new directing group pentafluorobenzoyl has been developed. The reaction proceeded efficiently in the presence of silver acetate as oxidant and chlorobenzene as solvent. A good range of benzylamines could be selectively monoalkenylated without interfering with further aza-Michael addition. The kinetic isotope effect experiments showed that C-H activation is not the rate-limiting step. In addition, a five-membered iridacycle species was isolated and established as the possible key intermediate.

Tandem Rh-Catalyzed Oxidative C-H Olefination and Cyclization of Enantiomerically Enriched Benzo-1,3-Sulfamidates: Stereoselective Synthesis of trans-1,3-Disubstituted Isoindolines

A tandem process, involving Rh(III)-catalyzed oxidative C-H olefination of enantiomerically enriched 4-aryl-benzo-1,3-sulfamidates and subsequent intramolecular aza-Michael cyclization has been developed. The reaction produces trans-benzosulfamidate-fused-1,3-disubstituted isoindolines as major products, in which the configurational integrity of the stereogenic center in the starting material is preserved. Further transformations of the benzosulfamidate-fused-1,3-disubstituted isoindolines are described.

Synthesis of TMPA Derivatives through Sequential Ir(III)-Catalyzed C-H Alkylation and Their Antidiabetic Evaluation

The synthesis and antidiabetic evaluation of ethyl 2-[2,3,4-trimethoxy-6-(1-octanoyl)phenyl]acetate (TMPA) and its structural analogs are described. The construction of TMPA derivatives has been successfully achieved in only two steps, which involve the iridium(III)-catalyzed α-alkylation of acetophenones with alcohols and the ketone-directed iridium(III)- or rhodium(III)-catalyzed redox-neutral C-H alkylation of α-alkylated acetophenones using Meldrum's diazo compounds. This synthetic protocol efficiently provides a range of TMPA derivatives with site selectivity and functional group compatibility. In addition, the site-selective demethylation of TMPA derivative affords the naturally occurring phomopsin C in good yield. Moreover, all synthetic compounds were screened for in vitro adenosine 5'-monophosphate-activated protein kinase (AMPK) activation using HepG2 cells. Furthermore, TMPA (5ac) and 5cd showing the most potent AMPK activation were treated for the in vivo antidiabetic experiment. Notably, our synthetic compound 5cd was found to display the powerful antidiabetic effect, stronger than that of metformin and TMPA (5ac).

Rh(III)-Catalyzed meta-C-H Olefination Directed by a Nitrile Template

A range of Rh(III)-catalyzed ortho-C-H functionalizations have been developed; however, extension of this reactivity to remote C-H functionalizations through large-ring rhodacyclic intermediates has yet to be demonstrated. Herein we report the first example of the use of a U-shaped nitrile template to direct Rh(III)-catalyzed remote meta-C-H activation via a postulated 12-membered macrocyclic intermediate. Because the ligands used for Rh(III) catalysts are significantly different from those of Pd(II) catalysts, this offers new opportunities for future development of ligand-promoted meta-C-H activation reactions.

Stereoselective synthesis of 1,3-disubstituted isoindolines via Rh(iii)-catalyzed tandem oxidative olefination–cyclization of 4-aryl cyclic sulfamidates

Rh(iii)-catalyzed tandem ortho C–H activation/olefination of 4-aryl cyclic sulfamidates and subsequent intramolecular cyclization which lead to the stereoselective synthesis of trans-1,3-disubstituted isoindolines are reported.

Rh(iii)-catalyzed C-H olefination of N-pentafluoroaryl benzamides using air as the sole oxidant

The oxidative olefination of a broad array of arenes and heteroarenes with a variety of activated and unactivated olefins has be achieved via a rhodium(iii)-catalyzed C-H activation reaction. The use of an N-pentafluorophenyl benzamide directing group is crucial for achieving catalytic turnovers in the presence of air as the sole oxidant without using a co-oxidant.

Direct C–H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis

The rhodium(iii)-catalyzed direct functionalization of aniline C–H bonds with α-diazo compounds for the preparation of ortho-alkylated anilines and highly substituted indoles is described.

Ruthenium-catalyzed oxidative coupling of 2-aryl-4-quinazolinones with olefins: synthesis of pyrrolo[2,1-b]quinazolin-9(1H)-one motifs

A ruthenium-catalyzed oxidative coupling of 2-aryl-quinazolinones with olefins via C–H bond activation followed by an intramolecular aza-Michael reaction is described.

Rh(III)-catalyzed oxidative coupling of 1,2-disubstituted arylhydrazines and olefins: a new strategy for 2,3-dihydro-1H-indazoles

A rhodium(III)-catalyzed oxidative olefination of 1,2-disubstituted arylhydrazines with alkenes via sp(2) C-H bond activation followed by an intramolecular aza-Michael reaction is described. This strategy allows the direct and efficient construction of highly substituted 2,3-dihydro-1H-indazole scaffolds.

Rh(iii)-catalyzed tandem oxidative olefination-cyclization of aryl sulfonamides

An efficient Rh(iii)-catalyzed ortho-selective C–H activation and tandem oxidative olefination-cyclization of aryl sulfonamides is described. The protocol has been applied to various substrates with good functional group tolerance.