Lewis Acid Controlled Regioselectivity in Styrene Hydrocyanation

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.

Nickel-catalyzed highly regioselective hydrocyanation of alkenes with Zn(CN)2

The first general and regioselective nickel-catalyzed hydrocyanation of terminal alkenes with Zn(CN)₂ using an air-stable and inexpensive nickel(ii) salt as the precatalyst has been developed.

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.

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).

Theoretical studies on vibrational spectra of some aluminum halides: Effect of theoretical methods and basis sets

The vibrational spectra of aluminum halides, AlX(3) (X=F, Cl, Br and I) and their dimers, Al(2)X(6), have been systematically investigated by ab initio restricted Hartree-Fock (RHF) and density functional B3LYP and B3P86 methods with LanL2DZ, SDD, CEP-31G and DGDZVP basis sets. The optimized geometries, calculated vibrational frequencies were evaluated via comparing with the experimental data. The vibrational frequencies, calculated by these methods with different basis sets, were compared to each other. The effect of the methods and the basis sets used on the calculated vibrational frequencies was discussed. The best fittings values between the calculated and the measured vibrational frequencies were achieved by B3LYP/DGDZVP theoretical level, with this method, the deviations are less than 2% for Al-X stretching vibrational modes in AlX(3) and less than 4% for Al-X stretching vibrational modes in Al(2)X(6). Some vibrational frequencies of Al(III) halides were predicted.