Highly Selective Hydrocyanation of Butadiene toward 3-Pentenenitrile

Synthesis, bridgehead functionalization, and photoisomerization of 9,10-diboratatriptycene dianions

9,10-Diboratatriptycene salts M2[RB(μ-C6H4)3BR] (R = H, Me; M+ = Li+, K+, [n-Bu4N]+) have been synthesized via [4 + 2] cycloaddition between doubly reduced 9,10-dihydro-9,10-diboraanthracenes M2[DBA] and benzyne, generated in situ from C6H5F and C6H5Li or LiN(i-Pr)2. [HB(μ-C6H4)3BH]2- reacts with CH2Cl2 to form quantitatively the bridgehead-derivatized [ClB(μ-C6H4)3BCl]2-, while twofold H- abstraction with B(C6F5)3 in the presence of SMe2 leads cleanly to the diadduct (Me2S)B(μ-C6H4)3B(SMe2). Photoisomerization of K2[HB(μ-C6H4)3BH] (THF, medium-pressure Hg lamp) provides facile access to diborabenzo[a]fluoranthenes, a little explored form of boron-doped polycyclic aromatic hydrocarbons. According to DFT calculations, the underlying reaction mechanism consists of three main steps: (i) photoinduced di-π-borate rearrangement, (ii) "walk reaction" of a BH unit, and (iii) boryl anion-like C-H activation.

Chiral Iodotriptycenes: Synthesis and Catalytic Applications

New iodotriptycenes, including some chiral derivatives, have been synthesised, and their catalytic potential towards oxidative transformations has been investigated. The enantioselectivities observed in the products using chiral iodotriptycene catalysts are low, probably owing to the large distances between the coordinating groups and the iodine moieties in these compounds.

Synthesis of adiponitrile from dimethyl adipate and ammonia in the vapor-phase over niobium oxide

An environmentally benign route leading to adiponitrile (ADN), a nylon-6,6 intermediate, was achieved by direct vapor-phase nitrilation of dimethyl adipate (DMA) with ammonia (NH3) in a fixed-bed reactor.

Triptycene Derivatives: From Their Synthesis to Their Unique Properties

Since the first preparation of triptycene, great progress has been made with respect to its synthesis and the understanding of its properties. Interest in triptycene-based systems is intense; in recent years, advances in the synthetic methodology and properties of new triptycenes have been reported by researchers from various fields of science. Here, an account of these new developments is given and placed in reference to earlier pivotal works that underpin the field. First, we discuss new approaches to the synthesis of new triptycenes. Progress in the regioselective synthesis of sterically demanding systems is discussed. The application of triptycenes in catalysis is also presented. Next, progress in the understanding of the relations between triptycene structures and their properties is discussed. The unique properties of triptycenes in the liquid and solid states are elaborated. Unique interactions, which involve triptycene molecular scaffolds, are presented. Molecular interactions within a triptycene unit, as well as between triptycenes or triptycenes and other molecules, are also evaluated. In particular, the summary of the synthesis and useful features will be helpful to researchers who are using triptycenes as building blocks in the chemical and materials sciences.

Cu-catalyzed cyanomethylation of imines and α,β-alkenes with acetonitrile and its derivatives

We describe copper-catalyzed cyanomethylation of imines and α,β-alkenes with a methylnitrile source and provide an efficient route to synthesize arylacrylonitriles and β,γ-unsaturated nitriles. This method tolerates aliphatic and aromatic alkenes substituted with a variety of functional groups such as F, Cl, Br, Me, OMe, tert-Bu, NO2, NH2 and CO2H with good to excellent yields (69-98%). These systems consist of inexpensive, simple copper catalyst and acetonitrile with its derivatives (α-bromo/α-iodo-acetonitrile) and are highly applicable in the industrial production of acrylonitriles.

Nickel-catalyzed highly regioselective hydrocyanation of aliphatic allenes

A nickel-catalyzed hydrocyanation of aliphatic allenes with excellent regioselectivity is developed. This protocol enables a catalytic pathway to access various allylic nitriles containing quaternary carbon centers in good yields.

Regioselective Arylboration of 1,3-Butadiene

A method for the regioselective 1,2-arylboration of 1,3-butadiene, a feedstock chemical, is reported. The reactions result in the formation of products that can be easily elaborated to other structures. The mechanistic details of this process are also discussed.

A Monophosphine Ligand Derived from Anthracene Photodimer: Synthetic Applications for Palladium-Catalyzed Coupling Reactions

Herein, we present an air-stable dianthracenyl monophosphine ligand (diAnthPhos) which can be prepared in two steps from commercially available anthracene derivatives. The ligand exhibits excellent efficiency for palladium-catalyzed coupling reactions. In particular, Miyaura borylation of heterocycle-containing electrophiles can be facilitated employing the diAnthPhos ligand with a broad substrate scope and low catalyst loading. The valuable synthetic utility of the new ligand is further demonstrated by a one-pot Miyaura borylation/Suzuki coupling protocol for heteroaryl-containing substrates.

HCN on Tap: On-Demand Continuous Production of Anhydrous HCN for Organic Synthesis

A continuous process for the on-demand generation, separation, and reaction of hydrogen cyanide (HCN) using membrane separation technology was developed. The inner tube of the reactor is manufactured from a gas-permeable, hydrophobic fluoropolymer (Teflon AF-2400) membrane. HCN is formed from aqueous reagents within the inner tube and then diffuses through the membrane into an outer tubing containing organic solvent. This technique enabled the safe handling of HCN for three different organic transformations without the need for distillation.

Synthesis and Electronic Properties of Triperyleno[3.3.3]Propellanes: Towards Two-Dimensional Electronic Structures

Threefold symmetric triperyleno[3.3.3]propellanes (TPRPs), which are composed of three perylene units peri-fused on [3.3.3]proppellane, have been synthesized and their electronic properties characterized. Unsubstituted TPRP assembles into two-dimensional honeycomb-like networks. TPRP displays a bathochromic-shifted absorption band in its absorption spectrum and shows well-separated one-electron redox waves in a cyclic voltammogram, due to a homoconjugative interaction between perylene moieties. A radical cation species of tert-butyl substituted TPRP shows spin delocalization over the whole of the molecule, which is derived from effective overlap of HOMOs among three perylene moieties.

Cu-Catalyzed atom transfer radical addition reactions of alkenes with α-bromoacetonitrile

A practical, simple, and efficient copper-catalyzed atom transfer radical addition reaction of alkenes with α-bromoacetonitrile is realized. With this methodology, various γ-bromonitriles and β,γ-unsaturated nitriles were efficiently constructed.

Electrophilic cyanation of allylic boranes: synthesis of β,γ-unsaturated nitriles containing allylic quaternary carbon centers

The electrophilic cyanation of allylic boranes, a process that enables the construction of allylic quaternary carbon centers, is reported.

Cooperative Palladium/Lewis Acid-Catalyzed Transfer Hydrocyanation of Alkenes and Alkynes Using 1-Methylcyclohexa-2,5-diene-1-carbonitrile

Catalytic transfer hydrocyanation represents a clean and safe alternative to hydrocyanation processes using toxic HCN gas. Such reactions provide access to pharmaceutically important nitrile derivatives starting with alkenes and alkynes. Herein, an efficient and practical cooperative palladium/Lewis acid-catalyzed transfer hydrocyanation of alkenes and alkynes is presented using 1-methylcyclohexa-2,5-diene-1-carbonitrile as a benign and readily available HCN source. A large set of nitrile derivatives (>50 examples) are prepared from both aliphatic and aromatic alkenes with good to excellent anti-Markovnikov selectivity. A range of aliphatic alkenes engage in selective hydrocyanation to provide the corresponding nitriles. The introduced method is useful for chain walking hydrocyanation of internal alkenes to afford terminal nitriles in good regioselectivities. This protocol is also applicable to late-stage modification of bioactive molecules.

Syntheses, Structures, and Characterization of Nickel(II) Stibines: Steric and Electronic Rationale for Metal Deposition

Reactions of the homoleptic and heteroleptic antimony ligands Sb ⁱPr₃, Sb ⁱPr₂Ph, SbMe₂Ph, and SbMePh₂ with NiI₂ generate rare Ni^II stibine complexes in either square planar or trigonal bipyramidal (TBP) geometries, depending on the steric size of the ligands. Tolman electronic parameters were calculated (DFT) for each antimony ligand to provide a tabulated resource for the relative strengths of simple antimony ligands. The electronic absorbance spectra of the square planar complexes exhibit characteristic bands [λ_max ≈ 560 nm (17 900 cm^-1), ε ≈ 4330 M^-1 cm^-1] at lower energies compared to the reported phosphine complexes, indicating the weak donor strength of the stibine ligands and resultant low-energy ligand field d→ d transitions. The square planar complex Ni(I)₂(Sb ⁱPr₃)₂ reacts with CO to form the TBP complex Ni(I)₂(Sb ⁱPr₃)₂(CO). Lastly, the complexes were investigated for nickel metal deposition on Si|Cu(100 nm) substrates. The complexes with the strongest donating ligand, Sb ⁱPr₃, deposited the purest layer of NiCu alloy according to the balanced reaction Ni(I)₂(Sb^{III i}Pr₃)₂ → Ni⁰ + Sb^V( ⁱPr₃)I₂; the iodinated Sb^V byproduct was unambiguously detected in the supernatant by ¹H NMR and mass spectrometry. Complexes with weaker ligands (poor I₂ acceptors/scavengers) resulted undesired deposition of iodine and CuI on the surface. This work thus serves as a guide for the design and synthesis of 3 d metal complexes with neutral, heavy main-group donors that are useful for metal deposition applications.

Pentiptycene-based concave NHC-metal complexes

The reaction of 1-amino,4-hydroxy-pentiptycene with diacetyl or acenaphthene-1,2-dione gave the respective diimines, followed by alkylation of the hydroxyl groups, and cyclization of the alkylated diimines to the respective bispentiptycene-imidazolium salts NHC·HCl. The azolium salts, being precursors to N-heterocyclic carbenes, were converted into metal complexes [(NHC)MX] (MX = CuI, AgCl, AuCl) and [(NHC)IrCl(cod)] and [(NHC)IrCl(CO)2] in good yields. In the solid state [(NHC)AgCl] displays a bowl-shaped structure of the ligand with the metal center buried within the concave unit.

Featuring Xantphos

This review highlights the use of the bisphosphine ligand group in homogeneous catalysis.

Ex situ generation of stoichiometric HCN and its application in the Pd-catalysed cyanation of aryl bromides: evidence for a transmetallation step between two oxidative addition Pd-complexes

A protocol for the Pd-catalysed cyanation of aryl bromides using near stoichiometric and gaseous hydrogen cyanide is reported for the first time. A two-chamber reactor was adopted for the safe liberation of ex situ generated HCN in a closed environment, which proved highly efficient in the Ni-catalysed hydrocyanation as the test reaction. Subsequently, this setup was exploited for converting a range of aryl and heteroaryl bromides (28 examples) directly into the corresponding benzonitriles in high yields, without the need for cyanide salts. Cyanation was achieved employing the Pd(0) precatalyst, P(tBu)3-Pd-G3 and a weak base, potassium acetate, in a dioxane-water solvent mixture. The methodology was also suitable for the synthesis of 13C-labelled benzonitriles with ex situ generated 13C-hydrogen cyanide. Stoichiometric studies with the metal complexes were undertaken to delineate the mechanism for this catalytic transformation. Treatment of Pd(P(tBu)3)2 with H13CN in THF provided two Pd-hydride complexes, (P(tBu)3)2Pd(H)(13CN), and [(P(tBu)3)Pd(H)]2Pd(13CN)4, both of which were isolated and characterised by NMR spectroscopy and X-ray crystal structure analysis. When the same reaction was performed in a THF : water mixture in the presence of KOAc, only (P(tBu)3)2Pd(H)(13CN) was formed. Subjection of this cyano hydride metal complex with the oxidative addition complex (P(tBu)3)Pd(Ph)(Br) in a 1 : 1 ratio in THF led to a transmetallation step with the formation of (P(tBu)3)2Pd(H)(Br) and 13C-benzonitrile from a reductive elimination step. These experiments suggest the possibility of a catalytic cycle involving initially the formation of two Pd(ii)-species from the oxidative addition of L n Pd(0) into HCN and an aryl bromide followed by a transmetallation step to L n Pd(Ar)(CN) and L n Pd(H)(Br), which both reductively eliminate, the latter in the presence of KOAc, to generate the benzonitrile and L n Pd(0).

Synthesis and Catalytic Applications of a Triptycene-Based Monophosphine Ligand for Palladium-Mediated Organic Transformations

1-Methoxy-8-(diphenylphosphino)triptycene (1), featuring high structural rigidity and steric bulkiness around the phosphine functionality, was synthesized as a new chiral monophosphine ligand for transition metal-catalyzed reactions. In the presence of 5-10 mol ppm (i.e., 0.0005-0.001 mol %) Pd(OAc)₂ and 1 (2 equiv for Pd), Suzuki-Miyaura cross-coupling reactions of aryl bromides and arylboronic acids proceeded effectively under mild atmospheric conditions to give the corresponding biaryl compounds in a high yield. The single-crystal X-ray analysis of a Pd(II) complex of 1 revealed its coordination structure, in which two homochiral molecules form a dimer, suggesting that triptycene could provide a chiral environment for asymmetric organic transformations. In fact, optically active 1 obtained by optical resolution showed good enantioselectivity in the palladium-catalyzed asymmetric hydrosilylation of styrene, which represents, for the first time, the asymmetric catalytic activity of triptycene-based monophosphine ligands.

Direct Synthesis of Nitriles from Aldehydes and Hydroxylamine Hydrochloride Catalyzed by a HAP@AEPH2-SO3H Nanocatalyst

We describe an efficient method for the direct preparation of nitriles from aldehydes and hydroxylamine hydrochloride catalyzed by sulfonated nanohydroxyapatite functionalized by 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-SO3H) as an eco-friendly and recyclable solid acid nanocatalyst. In this protocol the use of a solid acid nanocatalyst provides a green, useful, and rapid method for the preparation of nitriles in excellent yields. In addition, the notable feature of this methodolgy is that the synthesized nanocatalyst can be recovered and reused five times without any noticeable loss of efficiency.

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.