Metal-free synthesis of 3,3-disubstituted oxindoles via 1,2-alkylarylation of activated alkenes with alcohols

Photoredox aerobic oxidative cycliation of N-arylacrylamides with benzylalcohols

While the radical coupling/cyclization of N-arylacrylamides has been well established for the synthesis of functionalized oxindoles, in the present work, a visible-light-induced aerobic oxidative coupling/cyclization reaction of N-arylacrylamides with benzylalcohols has been developed. The combination of LiBr and benzophenone as the additive was found to be highly effective to enhance the catalytic efficacy. This protocol offers a mild alternative access to structurally valuable hydroxyalkyl oxindoles. Mechanistic studies reveal that the bromo radical in situ formed through the photoredox SET process under aerobic conditions enables efficient HAT to generate the key hydroxyalkyl radical intermediate.

Donor-Acceptor Complex Enables Cascade Radical Cyclization of N-Arylacrylamides with Katritzky Salts

Cascade radical cyclization of N-arylacrylamides is an attractive method to prepare 3,3-disubstituted oxindoles. As the reported methods often require additives and/or photocatalysts, we herein report an additive- and photocatalyst-free deaminative strategy for their synthesis under mild conditions, enabled by photoactivation of an electron donor-acceptor (EDA) complex. DFT studies indicated that the involvement of an explicit xylene solvent molecule can greatly enhance the photoactivity of the EDA complex between N-arylacrylamides and Katritzky salts.

Copper-promoted cyanoalkylation/ring-expansion of vinylcyclopropanes with α-C-H bonds in alkylnitriles toward 3,4-dihydronaphthalenes

A copper-promoted oxidative cyanomethylation/ring-expansion of vinylcyclopropanes with α-C(sp3)-H bonds in alkyl nitriles is established for the generation of 1-cyanoethylated 3,4-dihydronaphthalenes. This cyanomethylation/ring-expansion involves a radical pathway and proceeds via cyanomethyl radical formation, radical addition and ring-expansion. This ring-expansion strategy offers a highly atom-economical route for the construction of nitrile-containing 3,4-dihydronaphthalenes, which can be transformed into other useful products under simple conditions.

Ppm Cu Catalyst Enables tert-Alkylation Followed by C-H Cyclization To Synthesize Substituted Oxindoles

In this paper, we established highly efficient Cu-catalyzed tandem tert-alkylation C-H cyclization of α-bromocarbonyls and methacrylamides to produce substituted oxindoles. The maximum turnover number was up to 48 000 with reasonable yield. Although the catalyst loadings were very low, the reaction was not involving radical chain reaction. The resulting oxindoles were able to transform into aza-multicyclic compound via a reduction.

Copper-catalyzed oxidative coupling of quinoxalin-2(1H)-ones with alcohols: access to hydroxyalkylation of quinoxalin-2(1H)-ones

An efficient protocol for the synthesis of hydroxyl-containing quinoxalin-2(1H)-ones has been developed via the copper-catalyzed cross-coupling reaction of quinoxalin-2(1H)-ones with alcohols with moderate to good yields.

Various difunctionalizations of acrylamide: an efficient approach to synthesize oxindoles

In this review, we summarize the advancement and applications in the difunctionalization of acrylamide to synthesize oxindoles based on the mechanism.

Copper-catalyzed alkylarylation of activated alkenes using isocyanides as the alkyl source: an efficient radical access to 3,3-dialkylated oxindoles

A novel copper-catalyzed oxidative cyclization of N-arylacrylamides for the synthesis of 3,3-dialkylated oxindoles is described using isocyanides as alkyl radical precursors.

Oxidative radical 1,2-alkylarylation of alkenes with α-C(sp3)–H bonds of acetonitriles involving 1,2-aryl migration

The first access to acyclic molecules by metal-free oxidative 1,2-alkylarylation of alkenes with acetonitriles is presented.

Metal-free direct cyanoisopropylation/arylation of N-arylacrylamides or N-alkyl-N-(arylsulfonyl)acrylamides with AIBN: a simple and mild approach to cyano-containing oxindoles

A general, highly efficient approach to cyano-containing oxindoles is presented that is achieved by a metal-free direct cyanoisopropylation/arylation ofN-arylacrylamides orN-alkyl-N-(arylsulfonyl)acrylamides with AIBN.

Metal-free TBAI-catalyzed arylsulfonylation of activated alkenes with sulfonylhydrazides

An efficient approach to isoquinoline-1,3(2H,4H)-dione derivatives through metal-free oxidative arylsulfonylation of α,β-unsaturated imides with sulfonylhydrazides is developed.

N-(Acyloxy)phthalimides as tertiary alkyl radical precursors in the visible light photocatalyzed tandem radical cyclization of N-arylacrylamides to 3,3-dialkyl substituted oxindoles

A visible light promoted tandem radical cyclization of N-arylacrylamides 1 with N-(acyloxy)phthalimides 2 to 3,3-dialkyl substituted oxindoles 3 was developed. ​Compounds 2 can be used as the precursors of tertiary alkyl radical.

Transition-metal-free oxidative carboazidation of acrylamides via cascade C–N and C–C bond-forming reactions

A novel transition-metal-free oxidative carboazidation of acrylamides using inexpensive NaN₃ and K₂S₂O₈ was achieved, which not only provided an efficient method to prepare various N₃-substituted oxindoles, but also represented a novel strategy for C–N and C–C bond formation via a free-radical cascade process.

Iron-catalyzed radical aryldifluoromethylation of activated alkenes to difluoromethylated oxindoles

An iron-catalyzed aryldifluoromethylation of activated alkenes has been developed, which is a rare example where a cosolvent is used to improve the yield along with Fenton's reagent.

1,2-Alkylarylation of activated alkenes with dual C–H bonds of arenes and alkyl halides toward polyhalo-substituted oxindoles

Alkylarylation of N-arylacrylamides with alkyl halides through selective scission of the C(sp³)–H bond adjacent to halide atoms is presented.

Metal-free radical cascade dichloromethylation of activated alkenes using CH2Cl2: highly selective activation of the C–H bond

A dicumyl peroxide-initiated highly selective activation of the (sp³)C–H bond in dichloromethane (DCM, CH₂Cl₂) has been achieved, which allows efficient access to dichloronated oxindoles via a free-radical cascade process.