Copper-mediated transformation of organosilanes to nitriles with DMF and ammonium iodide

Phosphine-catalyzed hydroboration of propiolonitriles: access to (E)-1,2-vinylcyanotrifluoroborate derivatives

We report an organocatalytic trans hydroboration of 3-substituted-propiolonitriles. In the presence of catalytic amounts of tributylphosphine and pinacolborane, regioselective hydroboration of the internal triple bond proceeded in a stereoselective fashion under mild conditions to afford the corresponding (E)-1,2-vinylcyanoborane derivatives. The mechanism is proposed to occur through a 1,2-phosphine addition instead of a canonical 1,4-conjugate addition pathway.

Selective Synthesis of Substituted Pyridines and Pyrimidines through Cascade Annulation of Isopropene Derivatives

Diverse substituted pyridines and pyrimidines with high selectivity were obtained using a concise and efficient protocol developed herein. The reaction proceeds via metal-free cascade annulation of isopropene derivatives. Using isopropene derivatives as C3 synthons, NH₄I as the "N" source, and formaldehyde or dimethyl sulfoxide as the carbon source, this reaction realizes the efficient formation of intermolecular C-N and C-C bonds.

Insights into the chemistry and therapeutic potential of acrylonitrile derivatives

Acrylonitrile is a fascinating scaffold widely found in many natural products, drugs, and drug candidates with various biological activities. Several drug molecules such as entacapone, rilpivirine, teriflunomide, and so forth, bearing an acrylonitrile moiety have been marketed. In this review, diverse synthetic strategies for constructing desired acrylonitriles are discussed, and the different biological activities and medicinal significance of various acrylonitrile derivatives are critically evaluated. The information gathered is expected to provide rational guidance for the development of clinically useful agents from acrylonitriles.

Application of combined cyanide sources in cyanation reactions

The cyanation reaction is a key transformation due to the wide-ranging applications of nitrile compounds in organic chemistry. Traditionally, the cyanation reaction employs metal cyanides as cyanide sources, which are toxic and environmentally unfriendly. Very recently, many excellent examples of using combined cyanide sources as cyanating agents have been reported. This review summarizes the applications of combined cyano-group sources in a variety of cyanation reactions.

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.

Photoassisted Charge Transfer Between DMF and Substrate: Facile and Selective N,N-Dimethylamination of Fluoroarenes

A reversible Van der Waals complex formation between the electron-deficient fluorinated aromatic ring and N,N-dimethylformamide (DMF) molecules followed by light irradiation resulted in charge transfer (CT) process. The complex was stabilized by ammonium formate and further decomposed to form the C-N bond. Control experiments revealed that the simultaneous S_N Ar pathway also contributes to product formation. This methodology is mild, metal-free, and effective for the amination of a variety of substrates. The reproducibility of this methodology was also verified on gram-scale reactions. The CT states were supported by control UV/Vis spectroscopy and computational studies.

Cu-Catalyzed Arylation of Bromo-Difluoro-Acetamides by Aryl Boronic Acids, Aryl Trialkoxysilanes and Dimethyl-Aryl-Sulfonium Salts: New Entries to Aromatic Amides

We describe a mechanism-guided discovery of a synthetic methodology that enables the preparation of aromatic amides from 2-bromo-2,2-difluoroacetamides utilizing a copper-catalyzed direct arylation. Readily available and structurally simple aryl precursors such as aryl boronic acids, aryl trialkoxysilanes and dimethyl-aryl-sulfonium salts were used as the source for the aryl substituents. The scope of the reactions was tested, and the reactions were insensitive to the electronic nature of the aryl groups, as both electron-rich and electron-deficient aryls were successfully introduced. A wide range of 2-bromo-2,2-difluoroacetamides as either aliphatic or aromatic secondary or tertiary amides were also reactive under the developed conditions. The described synthetic protocols displayed excellent efficiency and were successfully utilized for the expeditious preparation of diverse aromatic amides in good-to-excellent yields. The reactions were scaled up to gram quantities.

Revisiting the synthesis of aryl nitriles: a pivotal role of CAN

Facilitated by the dual role of Ceric Ammonium Nitrate (CAN), herein we report a cost-effective approach for the cyanation of aryl iodides/bromides with CAN-DMF as an addition to the existing pool of combined cyanation sources. In addition to being an oxidant, CAN acts as a source of nitrogen in our protocol. The reaction is catalyzed by a readily available Cu(ii) salt and the ability of CAN to generate ammonia in the reaction medium is utilized to eliminate the additional requirement of a nitrogen source, ligand, additive or toxic reagents. The mechanistic study suggests an evolution of CN- leading to the synthesis of a variety of aryl nitriles in moderate to good yields. The proposed mechanism is supported by a series of control reactions and labeling experiments.

Palladium-Catalyzed Hiyama Cross-Couplings of Arylsilanes with 3-Iodoazetidine: Synthesis of 3-Arylazetidines

The first palladium-catalyzed Hiyama cross-coupling reactions of arylsilanes with 3-iodoazetidine were described. The protocol provides a convenient access to a variety of useful 3-arylazetidines which are of great interest in pharmaceutical laboratories in moderate to good yields (30%-88%). In addition, this strategy has the advantage of easy operation and mild reaction conditions.

E- and Z-, di- and tri-substituted alkenyl nitriles through catalytic cross-metathesis

Nitriles are found in many bioactive compounds, and are among the most versatile functional groups in organic chemistry. Despite many notable recent advances, however, there are no approaches that may be used for preparation of di- or trisubstituted alkenyl nitriles. Related approaches which are broad in scope and can deliver the desired products in high stereoisomeric purity are especially scarce. Here, we describe the development of several efficient catalytic cross-metathesis strategies, which provide direct access to a considerable range of Z- or E-disubstituted cyano-substituted alkenes or their corresponding trisubstituted variants. Depending on the reaction type, a molybdenum-based monoaryloxide pyrrolide (MAP) or chloride (MAC) complex may be the optimal choice. The utility of the approach, enhanced by an easy-to-apply protocol for utilization of substrates bearing an alcohol or a carboxylic acid moiety, is highlighted in the context of applications to synthesis of biologically active compounds.

Non-toxic cyanide sources and cyanating agents

The present review gives an overview over non-toxic cyanation agents and cyanide sources used in the synthesis of structurally diverse products containing the nitrile function. Nucleophilic as well as electrophilic agents/systems that transfer the entire CN-group were taken in consideration. Reactions in which a preexisting carbon functionality is transformed into a nitrile function by addition of nitrogen are however not covered here.

Alkene hydroboration with pinacolborane catalysed by lithium diisobutyl-tert-butoxyaluminum hydride

Here we developed a highly efficient alkene hydroboration protocol, showing that various alkyl boronates can be smoothly obtained in good yields by reacting alkenes with pinacolborane (HBpin) in the presence of 5 mol% lithium diisobutyl-tert-butoxyaluminum hydride. The coordination of aluminate ions with lithium cations allowed for effective hydride transfer during hydroboration, and the obtained boronate ester was further used for C–C coupling, trifluoroboronate salt formation, and oxidation to alcohol.

Here we developed a highly efficient alkene hydroboration protocol, showing that various alkyl boronates can be smoothly obtained in good yields by reacting alkenes with pinacolborane (HBpin) in the presence of 5 mol% lithium diisobutyl-tert-butoxyaluminum hydride.

Beyond a solvent: triple roles of dimethylformamide in organic chemistry

N,N-Dimethylformamide (DMF) is frequently used as an aprotic solvent in chemical transformations in laboratories of academia as well as in those of chemical industry. In the present review, we will reveal that DMF is actually something much more than a solvent. It is a unique chemical since, as well as being an effective polar aprotic solvent, it can play three other important roles in organic chemistry. It can be used as a reagent, a catalyst, and a stabilizer.

Copper-mediated C–H cyanation of (hetero)arenes with ethyl (ethoxymethylene)cyanoacetate as a cyanating agent

A copper-mediated direct C–H cyanation reaction of (hetero)arenes with ethyl (ethoxymethylene)cyanoacetate as a safe cyanating agent has been developed.

Cyanation of aromatic/vinylic boronic acids with α-cyanoacetates

A protocol is reported to achieve safe and convenient aromatic and vinylic cyanation of boronic acids (as well as halides) with α-cyanoacetates, avoiding the use of toxic cyanide salts.

A copper(i)-catalyzed three-component reaction of triethoxysilanes, sulfur dioxide, and alkyl halides

A copper(i)-catalyzed three-component reaction of triethoxysilanes, DABCO·(SO₂)₂, and alkyl halides is reported. This transformation provides a facile route to sulfones under ligand-free conditions catalyzed by copper(i) oxide. The insertion of sulfur dioxide is efficient, and both triethoxyarylsilanes and triethoxyalkylsilanes are practicable during the coupling process.

A novel coupling reaction of α-halo ketones promoted by SmI3/CuI

In the presence of SmI₃ and catalyzed by CuI in DMF, α-haloketones were transformed unexpectedly into α-hydroxy-1,4-diketones. The mechanism was probed and DMF was assumed to play a dual role both as a hydroxyl source and as a solvent.

Copper-catalyzed decarboxylative cross-coupling of cinnamic acids and ACCN via single electron transfer

A novel and convenient method for the synthesis of β,γ-unsaturated nitriles using ACCN (1,1′-azobis(cyclohexane-1-carbonitrile)) as a cyano source was described.

C–H bond cyanation of arenes using N,N-dimethylformamide and NH4HCO3 as a CN source over a hydroxyapatite supported copper catalyst

Copper dispersed on Ca₅(PO₄)₃OH has been identified as an excellent heterogeneous catalyst for the in situ generation of ‘CN’ from NH₄HCO₃ and N,N-dimethylformamide, in the C–H bond activation of 2-phenylpyridine.

A general route to sulfones via insertion of sulfur dioxide promoted by cobalt oxide

A cobalt-promoted coupling reaction of triethoxysilanes, sulfur dioxide, and electrophiles is developed. Different electrophilic partners including alkyl bromides, iodonium salts, and electron-poor (hetero)aryl chlorides work well under the standard conditions.