Cu(II)-Catalyzed, Site Selective Sulfoximination to Indole and Indolines via Dual C-H/N-H Activation

Ruthenium(II)-Catalyzed C-H Activation/Annulation of 5-Phenyl-pyrroline-2-carboxylates with Alkynes: Synthesis of 2,3-Diphenylspiro-[indene-1,2'pyrrolidine]carboxylate Derivatives

While saturated nitrogen heterocycles are privileged scaffolds, their streamlined catalytic synthesis with unsymmetrical substitution patterns remains a daunting challenge. Herein, we report the ruthenium(II)-catalyzed synthesis of spiro[indene-proline] derivatives via C-H activation/annulation of 5-phenyl-pyrroline-2-carboxylates with alkynes. The protocol utilized imine coordination, resulting in high reaction yields with a wide range of functional group tolerance, scalability, and scaffold diversity. This annulation was successful even with various biologically active pharmacophores. The reaction featured a reversible C-H metalation step and suggested the possibility of a base-assisted internal electrophilic substitution pathway.

Cobalt-Catalyzed Regioselective C8-H Sulfoxamination of 1-Naphthylamine Derivatives with NH-Sulfoximines

A simple cobalt-catalyzed, picolinamide-directed C8-H sulfoxamination of 1-naphthalamides with NH-sulfoximines has been developed. This cross-dehydrogenative C-H/N-H coupling reaction offers a facile route to N-arylated sulfoximines, exhibiting high yields, a broad substrate scope, and excellent functional group tolerance and scalability.

Strategies for oxidative synthesis of N-triflyl sulfoximines

The oxidation of various structurally different N-trifluoromethylthio sulfoximines was investigated using different oxidizing agents and conditions. Mono- and disubstituted phenyl methyl and phenyl cyclopropyl N-trifluoromethylthio sulfoximines were oxidized with NaOCl·5H2O in water, while sterically hindered substrates bearing bulkier alkyl chains or two phenyl rings required the addition of MeCN to the reaction mixture. Chloro-, bromo-, and cyano-substituted substrates, as well as substrates bearing the benzyl groups, required a completely different approach using m-CPBA in DCM. Each method was tested on a gram-scale, with almost no difference in yield or reaction profile. The methods were also tested on N-p-tolylthio sulfoximine where successful oxidation to the corresponding sulfone derivative was observed. Finally, the N-triflyl sulfoximines acquired in the oxidations were examined in terms of stability and reactivity in Suzuki-Miyaura and Sonogashira coupling reactions, as well as many others. The selective mono- and dinitration of 4-methoxyphenyl N-triflyl sulfoximine was demonstrated by using nitric and sulfuric acid. N-triflyl sulfoximines were found to be stable in concentrated aqueous NaOH and HCl solutions and at elevated temperatures.

Cu(II)-Mediated Sulfonylation of (Hetero)arenes with TosMIC Using Monodentate Directing Groups

Monodentate chelation-assisted direct ortho-C-H sulfonylation of (hetero)arenes using TosMIC as the novel sulfonylating reagent has been developed. A broad range of substrates, including indolines, indoles, 2-phenylpyridines, and others were well tolerated to afford the corresponding products in moderate to good yields. Mechanistic studies revealed that the sulfonyl radical might be involved. Inspired by the above discovery, preliminary para-C-H sulfonylation of naphthalene substrate was also successfully realized. The current protocol featured with cheap metal catalysis, good functional group compatibility, and operational convenience.

Cobalt(III)-Catalyzed Directed C-7 Selective C-H Alkynylation of Indolines with Bromoalkynes

A cobalt(III)-catalyzed directed C-7 alkynylation of indolines with easily accessible bromoalkynes has been developed. The reaction has a broad substrate scope with excellent yields and represents a powerful route to the synthesis of 7-alkynyl-substituted indolines. In addition, the reaction can be extended to the coupling of N-aryl 7-azaindoles, highlighting the synthetic practicability of the strategy.