Access to α-Cyano Carbonyls Bearing a Quaternary Carbon Center by Reductive Cyanation

Ni-catalyzed reductive cyanation of alkenyl tosylates and triflates

Herein, we disclose the nickel-catalyzed reductive cyanation of alkenyl tosylates and triflates. Both cyclic and acyclic alkenyl nitriles are produced in moderate to good yield using 2-(4-methoxyphenyl)-2-methylmalononitrile (MeO-MPMN), a novel transnitrilation, or nitrile transfer, reagent. A robustness screen was undertaken to demonstrate the functional group tolerance of this method.

Forging structural complexity: diastereoselective synthesis of densely substituted β-lactams with dual functional handles for enhanced core modifications

The preparation of the β-lactam motif containing both C-Br and N-O bonds as functional handles remains an unmet synthetic challenge. Described herein is a novel and highly diastereoselective NBS-mediated cyclization of N-alkoxy α,β-unsaturated silyl imino ethers to furnish nearly three dozen α-bromo N-alkoxy β-lactams. The reaction gives rapid and convenient access to structurally diverse monocyclic, spirocyclic and fused β-lactams in moderate to good yields. The two functional handles were shown to be useful for the further elaboration of the β-lactam core.

Biocatalytic Synthesis of Nitrile-Bearing All-Carbon Quaternary Stereocenters

The synthesis of all-carbon quaternary stereocenters containing nitriles is a very important and challenging subject in organic chemistry. We used a biocatalytic approach under mild conditions to obtain new derivatives of these scaffolds by oxidation of catechols by Myceliophthora thermophila laccase (Novozym 51003) to afford o-quinones and 1,4-addition of a series of carbon nucleophiles containing tertiary alkyle nitriles to these intermediates. Using this approach, α-cyano carbonyls bearing a quaternary stereocenter were also prepared. Finally, the yields for the prepared compounds were 72-94%.

Nickel Catalyzed Selective Arylation of Geminal Dinitriles: Direct Access to α-Cyano Carbonyl Compounds

The catalytic intermolecular arylation of disubstituted geminal dinitriles with in situ generated arylnickel complexes is disclosed. This method efficiently provides various all-carbon substituted α-cyanocarbonyl compounds without additives and an inert atmosphere. It also demonstrates the arylation of R-BINOL and S-BINOL derived geminal dinitriles, preserving optical purity. Mechanistic studies proved that the in situ generated organonickel complex is involved in arylation.

Nickel-Catalyzed Reductive Alkyne Hydrocyanation Enabled by Malononitrile and a Formaldehyde Additive

The development of a nickel-catalyzed reductive alkyne hydrocyanation is described using 2-methyl-2-phenylmalononitrile (MPMN), a C-bound electrophilic transnitrilation reagent. Reproducibility issues led to the detection of oxidized hemiaminal impurities within N,N-dimethylacetamide. These impurities release formaldehyde in situ, which was ultimately identified as a critical reaction additive. A range of diaryl and aryl-alkyl alkynes underwent hydrocyanation. Mechanistic experiments revealed that formaldehyde and MPMN undergo a Ni-catalyzed reductive coupling of two π-components, leading to the controlled release of glycolonitrile as the active cyanating agent.

Synthesis of β-Ketonitriles via N-Heterocyclic-Carbene-Catalyzed Radical Coupling of Aldehydes and Azobis(isobutyronitrile)

Herein, an NHC (N-heterocyclic carbene)-catalyzed radical coupling reaction between aldehydes and azobis(isobutyronitrile) (AIBN) has been developed. This method provides an efficient and convenient approach for the synthesis of β-ketonitriles containing a quaternary carbon center (31 examples, up to >99% yield) utilizing commercially available substrates. This protocol features broad substrate scope, good functional group tolerance, and high efficiency under metal-free and mild reaction conditions.

Ni-Catalyzed enantioselective reductive arylcyanation/cyclization of N-(2-iodo-aryl) acrylamide

A Ni/(S,S)-BDPP-catalyzed intramolecular Heck cyclization of N-(2-iodo-aryl) acrylamide with 2-methyl-2-phenylmalononitrile was developed to give oxindoles with good enantioselectivities. We found that utilizing such an electrophilic cyanation reagent could tackle the deleterious effect of the coordinative cyanide ion in the asymmetric alkene arylcyanation.

α-Functionalization of ketones promoted by sunlight and heterogeneous catalysis in the aqueous phase

Herein, a protocol that combines heterogeneous catalysis and solar photocatalysis for the regioselective α-substitution of asymmetric ketones with quinoxalinones has been reported. The result indicates that the reaction is more likely to occur on the α-carbon. This strategy provides a green and efficient way for the α-functionalization of ketones. A singlet oxygen involved mechanism is suggested for the transformation.

Visible light-mediated synthesis of α-alkoxy/hydroxy diarylacetaldehydes from terminal alkynes

A visible light-mediated approach enabling the use of alcohols as nucleophiles in a one-step synthesis of α-alkoxy/hydroxy diarylacetaldehydes is reported.

Construction of CF3-Functionalized Fully Substituted Benzonitriles through Rauhut-Currier Reaction Initiated [3 + 3] Benzannulation

Though numerous cyanation reactions have been developed for the synthesis of benzonitriles, the construction of valuable fully substituted benzonitriles is still a challenging task. Herein, we reported a tertiary amine-catalyzed [3 + 3]-benzannulation for the green synthesis of CF₃-functionalized fully substituted benzonitriles. This strategy features exclusive chemoselectivity, high atom-economy, and good step-economy with environment-friendly reagents and mild conditions. Unique triphenyl-substituted dicyanobenzoate products could be rapidly constructed using this method. The practicality and reliability of this reaction were proved by the successful scale-up synthesis. A mechanistic study indicates that the [3 + 3]-benzannulation was initiated by an intermolecular Rauhut-Currier reaction.

A boron-nitrogen transborylation enabled, borane-catalysed reductive cyanation of enones

Cyanation offers a simple method for the introduction of a nitrile group into organic molecules and an orthogonal route for the installation of a wide array of functional groups using simple transformations. Cyanation methods are dominated by transition metal catalysis and the use of hydrogen cyanide gas. Here, the electrophilic cyanation of enones was achieved using a main-group catalyst and a non-toxic, electrophilic cyanide source. This protocol was applied across a broad substrate scope including those containing reducible functional groups. Mechanistic studies indicated an amino-borane intermediate which underwent B-N transborylation (B-N/B-H exchange) to achieve catalytic turnover.