tert-Butylhydroperoxide mediated radical cyanoalkylation/cyanoalkenylation of 2-anilino-1,4-naphthoquinones with vinylarenes/arylalkynes and azobis(alkylcarbonitrile)s

A novel sustainable methodology based on one-pot cyanoalkylation/cyanoalkenylation of 2-anilino-1,4-naphthoquinones with vinylarenes/arylalkynes and azobis(alkylcarbonitrile)s involving a three-component radical cascade pathway has been achieved. Here, tert-butylhydroperoxide (TBHP) acts as an efficient oxidant, and it smoothly drives the reaction, producing the three-component products in very good to excellent yields. This cascade reaction eliminates the use of any base, additive, metal and hazardous cyanating agent. Additionally, this protocol exclusively delivers a stereospecific product in the case of arylalkynes. The involvement of radicals is evidenced through various radical trapping experiments.

Metal-free three-component cyanoalkylation of quinoxalin-2(1H)-ones with vinylarenes and azobis(alkylcarbonitrile)s

A K2S2O8-mediated C3 cyanoalkylation of quinoxalin-2(1H)-ones via a three-component radical cascade reaction with vinylarenes and azobis(alkylcarbonitrile)s has been achieved.

Photo-Promoted Decarboxylative Alkylation of α,β-Unsaturated Carboxylic Acids with ICH2CN for the Synthesis of β,γ-Unsaturated Nitriles

An efficient, catalyst/photocatalyst-free, and cost-effective methodology for the decarboxylative alkylation of α,β-unsaturated carboxylic acids to synthesize β,γ-unsaturated nitriles has been developed. The reaction proceeded in an environmentally benign atmosphere of blue light-emitting diode irradiation with K₂CO₃ and water at room temperature. The methodology worked for a wide range of substrates (22 examples) with up to 83% yield. The protocol is also compatible for gram-scale synthesis.

Visible-Light-Induced Photocatalytic Oxidative Decarboxylation of Cinnamic Acids to 1,2-Diketones

A concerted metallophotoredox catalysis has been realized for the efficient decarboxylative functionalization of α,β-unsaturated carboxylic acids with aryl iodides in the presence of perylene bisimide dye to afford 1,2-diketones.

Cu-catalyzed cyanomethylation of imines and α,β-alkenes with acetonitrile and its derivatives

We describe copper-catalyzed cyanomethylation of imines and α,β-alkenes with a methylnitrile source and provide an efficient route to synthesize arylacrylonitriles and β,γ-unsaturated nitriles. This method tolerates aliphatic and aromatic alkenes substituted with a variety of functional groups such as F, Cl, Br, Me, OMe, tert-Bu, NO2, NH2 and CO2H with good to excellent yields (69-98%). These systems consist of inexpensive, simple copper catalyst and acetonitrile with its derivatives (α-bromo/α-iodo-acetonitrile) and are highly applicable in the industrial production of acrylonitriles.

Catalytic Claisen Rearrangement by Intercepting Ketenimines with Propargylic Alcohols: A Strategy to Generate and Transform Ketenimines from Radicals

An efficient strategy for facilitating the cross-coupling of two radicals has been established via the coordination of a radical with a metal catalyst. This strategy provides a remarkable ability to harness the reactivity of nitrile-containing azoalkanes and enables a novel cascade reaction with nitrile-containing azoalkanes and propargylic alcohols to be established. By using this reaction, a range of acetylenic and allenic amides were obtained that provides a versatile platform for further derivatizations.

Metal-Free-Catalyzed Synthesis of Allyl Nitriles via Csp2-Csp3 Coupling between Olefins and Azobis (Alkyl-carbonitrile)

The metal-free-catalyzed synthesis of allyl nitriles from C_sp²-C_sp³ coupling between olefins and azobis was carried out. Key on this work was that the synthesis of allyl nitriles directly using olefin as a starting material was considered to be more efficient and economical than the alkyne, alkynyl carboxylic acid, or cinnamic acid used in previous works. Moreover, in this reaction, iodine served as the sole promoter, azobis served as a cyanation reagent, and N₂ was the only nontoxic byproduct that could avoid the utilization of metal catalysts and virulent nitrile reagents and generation of toxic wastes. With an optimum condition in hand, more than 30 examples of desired products including aromatic and aliphatic nitriles have been synthesized in good to excellent yields. Based on control experiments and literature data, a plausible mechanism of cyanation was proposed.

Rhodium(i)-catalyzed C6-selective C-H alkenylation and polyenylation of 2-pyridones with alkenyl and conjugated polyenyl carboxylic acids

A versatile Rh(i)-catalyzed C6-selective decarbonylative C-H alkenylation of 2-pyridones with readily available, and inexpensive alkenyl carboxylic acids has been developed. This directed dehydrogenative cross-coupling reaction affords 6-alkenylated 2-pyridones that would otherwise be difficult to access using conventional C-H functionalization protocols. The reaction occurs with high efficiency and is tolerant of a broad range of functional groups. A wide scope of alkenyl carboxylic acids, including challenging conjugated polyene carboxylic acids, are amenable to this transformation and no addition of external oxidant is required. Mechanistic studies revealed that (1) Boc2O acts as the activator for the in situ transformation of the carboxylic acids into anhydrides before oxidative addition by the Rh catalyst, (2) a decarbonylation step is involved in the catalytic cycle, and (3) the C-H bond cleavage is likely the turnover-limiting step.

Iodine-promoted radical alkyl sulfuration of imidazopyridines with dialkyl azo compounds and elemental sulfur

Dialkyl azo compounds were found to be effective alkyl radical sources for direct alkyl sulfuration with imidazopyridines using elemental sulfur under metal-free conditions. Iodine, an inexpensive and mild reagent, could promote alkyl sulfuration. A variety of quaternary cyanoalkyl radicals were successfully coupled with elemental sulfur. A subsequent C-H sulfuration of imidazopyridines afforded a diverse array of imidazopyridine derivatives bearing cyanoalkylthio groups. The cyano group could be modified and further underwent condensation with 2-aminothiazole to afford an interesting heterocyclic amide. Control experiments showed that iodine could greatly suppress the self-coupling of cyanoalkyl radicals, thus making the sulfuration proceed smoothly.

Cu-Catalyzed atom transfer radical addition reactions of alkenes with α-bromoacetonitrile

A practical, simple, and efficient copper-catalyzed atom transfer radical addition reaction of alkenes with α-bromoacetonitrile is realized. With this methodology, various γ-bromonitriles and β,γ-unsaturated nitriles were efficiently constructed.

Electrophilic cyanation of allylic boranes: synthesis of β,γ-unsaturated nitriles containing allylic quaternary carbon centers

The electrophilic cyanation of allylic boranes, a process that enables the construction of allylic quaternary carbon centers, is reported.

Copper-catalyzed selective radical–radical cross-coupling for C–S bond formation: an access to α-alkylthionitriles

Oxidative radical–radical cross-coupling: a new protocol for C–S bond formation was developed by selective cross-coupling between a thiyl radical and an isobutyronitrile radical.

Cu(ii)-Mediated keto C(sp3)–H bond α-acyloxylation of N,N-dialkylamides with aromatic carboxylic acids

The first example of Cu(ii)-mediated oxidative coupling of aromatic carboxylic acids with the C(sp³)–H bond adjacent to the keto group of N,N-dialkylamides has been developed.

Copper-promoted [2+2+2] annulation of 1,n-enynes through decomposition of azobis(alkyl nitrile)s

The first copper-promoted 1,n-enyne [2+2+2] carbocyclization using azobis(alkyl nitrile)s as two-carbon units has been developed.

Copper-catalyzed decarboxylative stereospecific amidation of cinnamic acids with N-fluorobenzenesulfonimide

A copper-catalyzed decarboxylative coupling of cinnamic acids with N-fluorobenzenesulfonimide (NFSI), to give the substituted (E)-amination products stereospecifically, has been realized.