Electrochemically promoted oxidative α-cyanation of tertiary and secondary amines using cheap AIBN

TFA-catalyzed solvent-free dearomative cyanidation of isoquinoline using (Boc)2O as an acylation agent

A TFA-catalyzed dearomative cyanidation of isoquinoline is described, which provides a series of 1-cyanoisoquinolines in high yields under solvent-free conditions. This protocol is operated under mild and environmentally friendly conditions, utilizing readily available and cost-effective starting materials. The reaction features broad functional group compatibility, 100 mmol scale synthesis ability and operational simplicity, making it a significant potential approach for the synthesis of various biologically interesting isoquinolines via α C-cyanation.

eCyanation Using 5-Aminotetrazole As a Safer Electrophilic and Nucleophilic Cyanide Source

An electrochemical method for carrying out safer cyanation reactions is reported. The use of 5-aminotetrazole as a cyanide source enabled the successful electrogeneration of both electrophilic and nucleophilic cyanide sources. To demonstrate the versatility of the method, a variety of cyanation reactions were carried out, including the synthesis of cyanamides, N-heterocycles, and aromatic nitriles, as well as the nucleophilic addition of cyanides to a variety of electrophiles without the need to handle highly toxic cyanide salts. Finally, as a proof of concept for scalability, the cyanation methodology was rapidly transferred to a flow electrosynthesis setup, which demonstrated its potential for large-scale applications.

The Azobis(isobutyronitrile)-Promoted Oxidative Radical α-Cyanation of Imine under Atmospheric O2

Herein, we report an azobis(isobutyronitrile) (AIBN)-promoted radical α-cyanation of in situ formed imine under atmospheric O2. This oxidative radical addition (ORA) procedure proceeds with the sequential homocleavage of AIBN, extrusion of N2, and capture of O2 toward an O-centered radical, which is converted to a cyano radical by β-scission. Then, the insertion of the cyano radical into the imine C═N bond forms an aminyl radical, leading to α-cyano imine after 1,2-hydrogen atom transfer (HAT) and H abstraction. Such a transition-metal-free procedure features mild reaction conditions and a broad substrate scope, employing molecular O2 as a clean terminal oxidant.

Mn-Catalyzed Aerobic Oxidative α-Cyanation of Tertiary Amines Using Azo/Hydrazide Redox

Azo compounds such as diethyl azodicarboxylate have been used in oxidative coupling reactions to generate iminium ions from tertiary amines. However, the requirement of stoichiometric amounts of azo compounds limits their large-scale applications. Herein, we present an aerobic oxidative α-cyanation of tertiary amines using catalytic amounts of an azo compound or hydrazine. The developed protocol provides a practical and ecofriendly route for α-cyanated tertiary amines, using molecular oxygen as the terminal oxidant.

Electrooxidative C(sp3)-H Cyanation of Sparteine and Lupanine in Undivided Batch and Continuous-Flow Cells

Sparteine is widely used as a chiral ligand in asymmetric synthesis, but methods for providing efficient access to functionalized sparteine derivatives are still limited. Herein, we describe an electrochemical α-cyanation of sparteine-type bis-quinolizidine alkaloids. This method features commercially available setups for batch and single-pass continuous flow conditions, enabling easy gram scale synthesis of valuable racemic and enantiopure products. Moreover, insights into the selectivity of the reaction and overoxidation mechanisms are disclosed. This allows for the development of divergent oxidation pathways depending on the electrolysis conditions.

Metal-free photoanodes for C-H functionalization

Organic semiconductors, such as carbon nitride, when employed as powders, show attractive photocatalytic properties, but their photoelectrochemical performance suffers from low charge transport capability, charge carrier recombination, and self-oxidation. High film-substrate affinity and well-designed heterojunction structures may address these issues, achieved through advanced film generation techniques. Here, we introduce a spin coating pretreatment of a conductive substrate with a multipurpose polymer and a supramolecular precursor, followed by chemical vapor deposition for the synthesis of dual-layer carbon nitride photoelectrodes. These photoelectrodes are composed of a porous microtubular top layer and an interlayer between the porous film and the conductive substrate. The polymer improves the polymerization degree of carbon nitride and introduces C-C bonds to increase its electrical conductivity. These carbon nitride photoelectrodes exhibit state-of-the-art photoelectrochemical performance and achieve high yield in C-H functionalization. This carbon nitride photoelectrode synthesis strategy may be readily adapted to other reported processes to optimize their performance.

Paired Electrolysis Enabled Cyanation of Diaryl Diselenides with KSCN Leading to Aryl Selenocyanates

The first example of paired electrolysis-enabled cyanation of diaryl diselenides, with KSCN as the green cyanating agent, has been developed. A broad range of aryl selenocyanates can be efficiently synthesized under chemical-oxidant- and additive-free, energy-saving and mild conditions.

Ultrasound-assisted bromination of indazoles at the C3 position with dibromohydantoin

Bromoaryl compounds have attracted great attention in organic chemistry, especially for the synthesis of pharmaceutical intermediates. Herein, we demonstrated a novel and efficient bromination protocol of indazoles via C-H bond cleavage to give site-specific 3-bromide products that could be further employed as synthetic blocks to prepare drugs. The reaction used DBDMH as a bromine source, tolerated a wide range of indazoles, and finished in 30 min under mild, ultrasound-assisted conditions. Besides, preliminary mechanistic studies revealed that this approach was not a radical process.

Paired Electrolysis for Decarboxylative Cyanation: 4-CN-Pyridine, a Versatile Nitrile Source

A decarboxylative cyanation of amino acids under paired electrochemical reaction conditions has been developed. 4-CN-pyridine was found to be a new and effective cyanation reagent under catalyst-free conditions. Mechanistic studies support a nucleophilic reaction pathway, and the cyanation protocol can be applied to diverse substrates including N,N-dialkyl aniline and indole derivatives.

Electrosynthesis of S-thiocarbamates with disulfides as a sulfur source

An electrochemical oxidative synthesis of S-thiocarbamates by a carbamothioation reaction via a three-component coupling reaction (disulfide, water and isocyanide) is developed, which avoids the use of external oxidants and generates only hydrogen gas as the by-product. With NH₄I as the mediator and electrolyte, the desired S-thiocarbamates were obtained in good yields in an undivided cell at room temperature.