Palladium- or nickel-catalyzed reaction of alkynes with trimethylsilyl cyanide. A new synthesis of 5-aminopyrrole-2-carbonitriles

The reaction of alkynes with trimethylsilyl cyanide (1) in the presence of a palladium or nickel catalyst gave 5-aminopyrrole-2-carbonitriles in high yields with high regioselectivity.     

Palladium- and nickel-catalyzed aminations of aryl imidazolylsulfonates and sulfamates

A nickel complex derived from dppf, along with NaOt-Bu as the base, allowed for challenging aminations of aryl sulfamates. An improved functional group tolerance is observed in novel palladium-catalyzed aminations of imidazolylsulfonates with rac-BINAP as the ligand.     

Palladium- and nickel-catalyzed reaction of methylenecyclopropanes with trimethylsilyl cyanide1

Pd- and Ni-catalyzed reactions of methylenecyclopropanes with trimethylsilyl cyanide (1) give β-(cyanomethyl)allylsilanes and 1-(trimethylsilyl)methyl-1-cyclopropanecarbonitriles; the ratio of those depends on catalysts used and on the structure of substrates employed.     

Palladium- and nickel-catalyzed cross-couplings of unsaturated halides bearing relatively acidic protons with organozinc reagents

A wide range of polyfunctional aryl, heteroaryl, alkyl, and benzylic zinc reagents were coupled with unsaturated aryl halides bearing an acidic NH or OH proton, using Pd(OAc)2 (1 mol %) and S-Phos (2 mol %) as catalyst without the need of protecting groups. A similar nickel-catalyzed reaction is described. The relative kinetic basicity of organozinc compounds as well as their stability toward acidic protons is also described.     

Ligand-guided pathway selection in nickel-catalyzed couplings of enals and alkynes

Nickel-catalyzed couplings of enals and alkynes utilizing triethylborane as the reducing agent illustrate a significant dependence on ligand structure. Simple variation of monodentate phosphines allows selective access to alkylative couplings or reductive cycloadditions, while further variation of reaction conditions provides clean access to reductive couplings and redox-neutral couplings.     

Synthesis of riccardin B by nickel-catalyzed intramolecular cyclization

Riccardin B, a macrocyclic bis(bibenzyl) possessing cytotoxic activity, and its dehydroxy derivative were synthesized in high yields using the nickel-catalyzed intramolecular coupling of the acyclic precursors.     

Intramolecular cyanoboration of alkynes via activation of boron-cyanide bonds by transition metal catalysts

Cyano(dialkylamino)boryl ethers of homopropargylic alcohols undergo intramolecular addition of a B-CN bond across their carbon-carbon triple bonds (cyanoboration) in the presence of palladium and nickel catalysts, furnishing five-membered cyclic boryl ethers regioselectively in good yields via 5-exo cyclization. The products were transformed into highly substituted α,β-unsaturated nitriles via Suzuki-Miyaura coupling to aryl iodides, rhodium-catalyzed conjugative addition to methyl vinyl ketone, and rhodium-catalyzed protodeborylation.     

Amine-directed intramolecular hydroacylation of alkenes and alkynes

Medium-ring heterocycles are prepared via an amine-directed, rhodium(I)-catalyzed intramolecular hydroacylation. The presence of an allyl substituent on the amine accelerates the reaction and increases product yields.     

Catalytic and metal-free intramolecular hydroalkoxylation of alkynes

Benzyltrimethylammonium hydroxide act as an efficient metal-free catalyst for the intramolecular hydroalkoxylation of alkynes. Notably, the use of microwave irradiation allowed reaction to operate in only two minutes. Under optimized reaction conditions, linear alkynes bearing aryl and heteroaryl substituents were successfully cyclized with good level of stereoselectivity.     

Palladium-catalyzed intramolecular asymmetric hydroamination of alkynes

The Pd-catalyzed reaction of internal alkynes with tethered amino groups in the presence of PhCO2H and RENORPHOS as chiral phosphine ligand is reported. Various five- and six-membered nitrogen-containing heterocycles were obtained in good to high yield with moderate to high ee.     

Palladium-catalyzed intramolecular cyanoboration of allenes leading to the regioselective synthesis of β-cyanoallylboranes

Inter- and intramolecular addition of the boron-cyanide bond of cyanoboranes across a carbon-carbon double bond of allenes proceeded in the presence of palladium catalysts, affording allylboranes that bear a cyano group at the β-position regioselectively.     

Divergent intramolecular reactions between phosphines and alkynes

A divergent intramolecular reaction of phosphine tethered alkyne in protic solvent was developed.This provided a novel and simple access to a large variety of(Z)-alkenylphosphine oxides and phospholane oxides.Our preliminary studies suggested that these divergent reactions are closely related to the reaction condition and molecular structure.A possible mechanism of C-P bond cleavage of a pentacoordinated hydroxyphosphorane intermediate was proposed.     

Synthesis of trisubstituted olefins via nickel-catalyzed decarboxylative hydroalkylation of internal alkynes

A novel NiH-catalyzed decarboxylative hydroalkylation of internal alkynes has been developed. Trisubstituted olefins were obtained in moderate to good yields with good regioselectivities. The reaction involves cis addition of NiH to the internal alkyne. The reaction shows good functional-group tolerance.     

Ligand-directed reaction products in the nickel-catalyzed electrochemical carboxylation of terminal alkynes

The influence of a series of N and P ligands in the nickel-catalyzed electrochemical carboxylation of 1-octyne has been studied. Different carboxylic acids are obtained depending on the nature of the ancillary ligand, and results afford an example of high ligand-directed product specificity.     

Ligand-switchable directing effects of tethered alkenes in nickel-catalyzed additions to alkynes

Nickel-catalyzed reductive couplings of aldehydes with alkynes that contain tethered olefins are described, in which the degree and sense of regioselectivity are controlled by the length of the tether and the presence or absence of an additive. When the alkyne and alkene are separated by four bonds, very high (>95:5) regioselectivities are observed. Use of a monodentate phosphine as an additive leads to formation of the opposite regioisomer in equal and opposite selectivity (5: >95). These results provide strong evidence for an interaction between the remote alkene and the metal center during the regioselectivity-determining step and suggest that reactions with and without an additive proceed via fundamentally distinct mechanisms.     

Stereoselective synthesis of enynes by nickel-catalyzed cross-coupling of divinylic chalcogenides with alkynes

(Z,Z)- and (E,E)-divinylic selenides and telurides undergo direct coupling with terminal alkynes in the presence of a nickel/CuI catalyst at room temperature to give (Z)- and (E)-enyne systems in good yields and with complete retention of configuration.     

Ni-catalyzed intramolecular cycloaddition of methylenecyclopropanes to alkynes

Ni-catalyzed intramolecular cycloaddition of methylenecyclopropanes (MCPs) to arkylalkynes via proximal bond cleavage is reported. The reaction provides a facile route for the preparation of cyclopenta[a]indene derivatives.     

Ligand-dependent scope and divergent mechanistic behavior in nickel-catalyzed reductive couplings of aldehydes and alkynes

A new procedure for catalytic reductive coupling of aldehydes and alkynes has been developed. The procedure uses Ni(COD)2 with an imidazolium carbene ligand as the catalyst and triethylsilane as the reducing agent. A crossover deuterium-labeling experiment illustrated that variants involving trialkyl phosphines and imidazolium carbene ligands with a nickel catalyst proceed by different mechanisms.     

Isoindoles and dihydroisoquinolines by gold-catalyzed intramolecular hydroamination of alkynes

The title compounds are enantioselectively synthesized in just two preparative steps, making use of the Ugi-four-component reaction with an amino acid as chiral component, followed by a gold-catalyzed hydroamination.