Aerobic Oxidative Transformation of Primary Azides to Nitriles by Ruthenium Hydroxide Catalyst

Mg(OtBu)2-catalyzed C–H oxidation of α-azido arylethanones using TBHP as the oxidant and carbonyl oxygen source: facile access to primary α-ketoamides

A Mg(OtBu)2-catalyzed C(sp3)–H oxidation of α-azido arylethanones to straightforwardly produce primary α-ketoamides is presented.

Sulfonium ion-promoted traceless Schmidt reaction of alkyl azides

Schmidt reaction by sulfonium ions is described. General primary, secondary, and tertiary alkyl azides were converted to the corresponding carbonyl or imine compounds without any trace of the activators. This bond scission reaction through 1,2-migration of C-H and C-C bonds was accessible to the one-pot substitution reaction.

Heterogeneous photocatalysis of azides: extending nitrene photochemistry to longer wavelengths

The photodecomposition of azides to generate nitrenes usually requires wavelengths in the <300 nm region. In this study, we show that this reaction can be readily performed in the UVA region (368 nm) when catalyzed by Pd-decorated TiO2. In aqueous medium the reaction leads to amines, with water acting as the H source; however, in non-protic and non-nucleophilic media, such as acetonitrile, nitrenes recombine to yield azo compounds, while azirine-mediated trapping occurs in the presence of nucleophiles. The heterogeneous process facilitates catalyst separation while showing great chemoselectivity and high yields.

Copper- and DMF-mediated switchable oxidative C–H cyanation and formylation of imidazo[1,2-a]pyridines using ammonium iodide

The cyanation and formylation of imidazo[1,2-a]pyridines were developed under copper-mediated oxidative conditions using ammonium iodide and DMF as a nontoxic combined cyano-group source and DMF as a formylation reagent.

Recent developments in dehydration of primary amides to nitriles

Various dehydration methods available for the direct conversion of amides to the corresponding nitriles have been reviewed.

Allylic azides: synthesis, reactivity, and the Winstein rearrangement

Organic azides are useful synthetic intermediates, which demonstrate broad reactivity. Unlike most organic azides, allylic azides can spontaneously rearrange to form a mixture of isomers. This rearrangement has been named the Winstein rearrangement. Using allylic azides can result in low yields and azide racemization in some synthetic contexts due to the Winstein rearrangement. Effort has been made to understand the mechanism of the Winstein rearrangement and to take advantage of this process. Several guiding principles can be used to identify which azides will produce a mixture of isomers and which will resist rearrangement. Selective reaction conditions can be used to differentiate the azide isomers in a dynamic manner. This review covers all aspects of allylic azides including their synthesis, their reactivity, the mechanism of the Winstein rearrangement, and reactions that can selectively elaborate an azide isomer. This review covers the literature from Winstein's initial report to early 2019.

Acceptorless dehydrogenative construction of CN and CC bonds through catalytic aza-Wittig and Wittig reactions in the presence of an air-stable ruthenium pincer complex

Acceptorless dehydrogenative construction of CN and CC bonds catalysed by air-stable ruthenium complexes.

Catalytic Promiscuity of Galactose Oxidase: A Mild Synthesis of Nitriles from Alcohols, Air, and Ammonia

We report an unprecedented catalytically promiscuous activity of the copper-dependent enzyme galactose oxidase. The enzyme catalyses the one-pot conversion of alcohols into the related nitriles under mild reaction conditions in ammonium buffer, consuming ammonia as the source of nitrogen and dioxygen (from air at atmospheric pressure) as the only oxidant. Thus, this green method does not require either cyanide salts, toxic metals, or undesired oxidants in stoichiometric amounts. The substrate scope of the reaction includes benzyl and cinnamyl alcohols as well as 4- and 3-pyridylmethanol, giving access to valuable chemical compounds. The oxidation proceeds through oxidation from alcohol to aldehyde, in situ imine formation, and final direct oxidation to nitrile.

Highly efficient nitrobenzene and alkyl/aryl azide reduction in stainless steel jars without catalyst addition

Mechanochemically promoted reduction of nitro and azido derivatives may be successfully performed in stainless steel jars without catalyst addition.

Ethanol gas-phase ammoxidation to acetonitrile: the reactivity of supported vanadium oxide catalysts

The gas-phase ammoxidation of ethanol, a bio-based platform molecule, has been investigated as a possible more sustainable route for the production of acetonitrile, using supported vanadium oxide catalysts. The nature of the interaction between the support and the active species greatly affected the catalytic performance.

Toluene Dioxygenase-Catalysed Oxidation of Benzyl Azide to Benzonitrile: Mechanistic Insights for an Unprecedented Enzymatic Transformation

Enzymatic dioxygenation of benzyl azide by toluene dioxygenase (TDO) produces significant amounts of the cis-cyclohexadienediol derived from benzonitrile, along with the expected azido diols. We demonstrate that TDO catalyses the oxidation of benzyl azide to benzonitrile, which is further dioxygenated to produce the observed cis-diol. A proposed mechanism for this transformation involves initial benzylic monooxygenation followed by a nitrene-mediated rearrangement to form an oxime, which is further dehydrated to afford the nitrile. To the best of our knowledge, this is the first report of enzymatic oxidation of an alkyl azide to a nitrile. In addition, the described oxime-dehydration activity has not been reported for Rieske dioxygenases.

An aerobic Cu-mediated practical approach to aromatic nitriles using cyanide anions as the nitrogen source

A copper-catalyzed cyanation of aryl methyl ketones using cyanide anions as the nitrogen source was developed. The reaction showed a broad substrate scope with moderate to excellent yields.

A straightforward and versatile protocol for the direct conversion of benzylic azides to ketones and aldehydes

We report that the benzyl azido group is directly converted to carbonyls in good yields through a rapid hydrolysis (basic conditions) of benzylideneamides generated readily/efficiently in situ under a very simple procedure involving conventional reagents.

Efficient conversion of primary azides to aldehydes catalyzed by active site variants of myoglobin

The oxidation of primary azides to aldehydes constitutes a convenient but underdeveloped transformation for which no efficient methods are available. Here, we demonstrate that engineered variants of the hemoprotein myoglobin can catalyze this transformation with high efficiency (up to 8,500 turnovers) and selectivity across a range of structurally diverse aryl-substituted primary azides. Mutagenesis of the 'distal' histidine residue was particularly effective in enhancing the azide oxidation reactivity of myoglobin, enabling these reactions to proceed in good to excellent yields (37-89%) and to be carried out at a synthetically useful scale. Kinetic isotope effect, isotope labeling, and substrate binding experiments support a mechanism involving heme-catalyzed decomposition of the organic azide followed by alpha hydrogen deprotonation to generate an aldimine which, upon hydrolysis, releases the aldehyde product. This work provides the first example of a biocatalytic azide-to-aldehyde conversion and expands the range of non-native chemical transformations accessible through hemoprotein-mediated catalysis.

An efficient transformation of primary halides into nitriles through palladium-catalyzed hydrogen transfer reaction

Two-step one-pot transformation of primary halides into the corresponding nitriles is successfully achieved under mild conditions. In this protocol, acetone functions as both a solvent and a hydrogen acceptor.

Cu- or Fe-catalyzed C–H/C–C bond nitrogenation reactions for the direct synthesis of N-containing compounds

This tutorial account summarizes the recent progress in Cu- or Fe-catalyzed C–H/C–C bond nitrogenation reactions for the direct synthesis of N-containing compounds.

Formation and nitrile hydrogenation performance of Ru nanoparticles on a K-doped Al2O3 surface

Decarbonylation-promoted Ru nanoparticle formation from Ru₃(CO)₁₂ on a basic K-doped Al₂O₃ surface was investigated by in situ FT-IR and in situ XAFS. The prepared Ru nanoparticle acted as an efficient catalyst for nitrile hydrogenation to primary amine.

Direct approaches to nitriles via highly efficient nitrogenation strategy through C-H or C-C bond cleavage

Because of the importance of nitrogen-containing compounds in chemistry and biology, organic chemists have long focused on the development of novel methodologies for their synthesis. For example, nitrogen-containing compounds show up within functional materials, as top-selling drugs, and as bioactive molecules. To synthesize these compounds in a green and sustainable way, researchers have focused on the direct functionalization of hydrocarbons via C-H or C-C bond cleavage. Although researchers have made significant progress in the direct functionalization of simple hydrocarbons, direct C-N bond formation via C-H or C-C bond cleavage remains challenging, in part because of the unstable character of some N-nucleophiles under oxidative conditions. The nitriles are versatile building blocks and precursors in organic synthesis. Recently, chemists have achieved the direct C-H cyanation with toxic cyanide salts in the presence of stoichiometric metal oxidants. In this Account, we describe recent progress made by our group in nitrile synthesis. C-H or C-C bond cleavage is a key process in our strategy, and azides or DMF serve as the nitrogen source. In these reactions, we successfully realized direct nitrile synthesis using a variety of hydrocarbon groups as nitrile precursors, including methyl, alkenyl, and alkynyl groups. We could carry out C(sp(3))-H functionalization on benzylic, allylic, and propargylic C-H bonds to produce diverse valuable synthetic nitriles. Mild oxidation of C═C double-bonds and C≡C triple-bonds also produced nitriles. The incorporation of nitrogen within the carbon skeleton typically involved the participation of azide reagents. Although some mechanistic details remain unclear, studies of these nitrogenation reactions implicate the involvement of a cation or radical intermediate, and an oxidative rearrangement of azide intermediate produced the nitrile. We also explored environmentally friendly oxidants, such as molecular oxygen, to make our synthetic strategy more attractive. Our direct nitrile synthesis methodologies have potential applications in the synthesis of biologically active molecules and drug candidates.

Palladium-catalyzed regioselective azidation of allylic C–H bonds under atmospheric pressure of dioxygen

A palladium-catalyzed allylic azidation of alkenes with sodium azide under atmospheric pressure of dioxygen was developed.