Synthesis of Aromatic Nitriles Using Nonmetallic Cyano-Group Sources

Solid-state Reaction of Azolium Hydrohalogen Salts with Silver Dicyanamide--Unexpected Formation of Cyanoguanidine-azoles, Reaction Mechanism and Their Hypergolic Properties

Cyanoguanidines as well as azoles are important bioactive groups, which play an important role in the medical application; meanwhile, the high nitrogen content makes them excellent backbones for energetic materials. A Novel and simple method that combined these two fragments into one molecular compound was developed through the transformation of dicyanamide ionic salts. In return, compounds 4–11 were synthesized, and fully characterized by IR, MS, NMR and elemental analysis. Meanwhile, the structures of compounds 4, 8 and 11 were confirmed by X-ray crystal diffraction. Detailed reaction mechanisms were studied through accurate calculations on the reaction energy profiles of the azolium cations and DCA anion, which revealed the essence of the transformation proceeding. Meanwhile, compound 8 exhibits excellent hypergolic property, which could be potentially novel molecular hypergolic fuel.

Straightforward synthesis of 1,2-dicyanoalkanes from nitroalkenes and silyl cyanide mediated by tetrabutylammonium fluoride

A straightforward synthesis of 1,2-dicyanoalkanes by reacting nitroalkenes with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride is described. The reaction proceeds through a tandem double Michael addition under mild conditions. Employing the hypervalent silicate generated from trimethylsilyl cyanide and tetrabutylammonium fluoride is essential for achieving this transformation. Mechanistic studies suggest that a small amount of water included in the reaction media plays a key role. This protocol is applicable to various types of substrates including electron-rich and electron-deficient aromatic nitroalkenes, and aliphatic nitroalkenes. Moreover, vinyl sulfones were found to be good alternatives, particularly for electron-deficient nitroalkenes. The broad substrate scope and functional group tolerance of the reaction makes this approach a practical method for the synthesis of valuable 1,2-dicyanoalkanes.

Sandmeyer cyanation of arenediazonium tetrafluoroborate using acetonitrile as a cyanide source

Palladium-catalyzed cyanation of aryldiazonium tetrafluoroborate using acetonitrile as a non-metallic cyanide source was achieved in the presence of Ag₂O under ambient air, eliminating the involvement of highly toxic CuCN used in the traditional Sandmeyer reaction, in which the CN group comes from metallic cyanides.

Rhodium(iii)-catalyzed cyanation of vinylic C–H bonds: N-cyano-N-phenyl-p-toluenesulfonamide as a cyanation reagent

Rh(iii)-catalyzed direct vinylic C–H cyanation reaction has been developed as a practical method for the synthesis of alkenyl nitriles.

Iodine-catalyzed ammoxidation of methyl arenes

A metal-free direct ammoxidation of readily available methyl arenes leading to nitriles was established under mild conditions.

Transition-metal-free cross-coupling of thioethers with aryl(cyano)iodonium triflates: a facile and efficient method for the one-pot synthesis of thiocyanates

A novel transition-metal-free method for the one-step synthesis of thiocyanates via the C–S bond cleavage of readily available thioethers was developed.

Copper-mediated three-component synthesis of 3-cyanoimidazo[1,2-a]pyridines

A copper-mediated three-component approach towards the synthesis of 3-cyanoimidazo[1,2-a]pyridines from 2-aminopyridines, acetophenones and benzyl cyanide was developed. This cascade reaction proceeds through a copper-mediated oxidative release of cyanide from benzyl cyanide, a copper-mediated Ortoleva–King reaction, and a copper-catalyzed cyanation.

Enantioselective conjugate addition of cyanide to chalcones catalyzed by a magnesium-Py-BINMOL complex

An efficient asymmetric conjugate addition of trimethylsilyl cyanide (TMSCN) to chalcones, catalyzed by bifunctional Py-BINMOL-Mg complex, with moderate to good enantioselectivities and in good yields, has been realized in this work.

Copper-mediated cyanation of indoles and electron-rich arenes using DMF as a single surrogate

The copper-mediated cyanation of indoles with DMF as a single surrogate of “CN” has been realized.

Cu(NO3)2·3H2O-mediated cyanation of aryl iodides and bromides using DMF as a single surrogate of cyanide

Cyanation of aryl iodides and bromides were approached by using DMF as a single source of “CN” in the presence of cheap Cu(NO₃)₂·3H₂O.

Copper-catalyzed cyanation of aryl iodides with α-cyanoacetates via C–CN bond activation

A mild copper-catalyzed cyanation of aryl iodides using readily available and friendly α-cyanoacetates as the CN source is reported.

Co(III)-catalyzed C-H activation/formal SN-type reactions: selective and efficient cyanation, halogenation, and allylation

The first cobalt-catalyzed cyanation, halogenation, and allylation via C-H activation have been realized. These formal SN-type reactions generate valuable (hetero)aryl/alkenyl nitriles, iodides, and bromides as well as allylated indoles using a bench-stable Co(III) catalyst. High regio- and mono-selectivity were achieved for these reactions. Additionally, allylation proceeded efficiently with a turnover number of 2200 at room temperature, which is unprecedented for this Co(III) catalyst. Alkenyl substrates and amides have been successfully utilized in Cp*Co(III)-catalyzed C-H activation for the first time.

Synthesis of nitriles via palladium-catalyzed water shuffling from amides to acetonitrile

Palladium-catalyzed synthesis of nitriles from amides has been described. Two similar, but complementary reaction conditions have been identified to convert various amides including α,β,γ,δ-unsaturated amides, cinnamides, aromatic amides and alkyl amides to the corresponding nitriles in good to excellent yield.

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.

Recent advances in transition-metal-catalyzed C–CN bond activations

Recent advances in transition-metal-catalyzed C–CN bond activation, leading to a lot of important approaches such as cyanofunctionalization, cross-coupling and cyanation, are reviewed.

Rhodium-catalyzed ortho-cyanation of symmetrical azobenzenes with N-cyano-N-phenyl-p-toluenesulfonamide

A rhodium(iii)-catalyzed ortho-cyanation of symmetrical azobenzenes with NCTS via azo-group-directed C(sp²)–H bond activation is described.

Chopping unfunctionalized carbon–carbon bonds: a new paradigm for the synthesis of organonitriles

Chopping of carbon–carbon bonds was very recently shown to be an efficient new strategy for the synthesis of organonitriles, as developed in this Highlight.