Copper(I)-Catalyzed Synthesis of Unsymmetrical All-Carbon Bis-Quaternary Centers at the Opposing α-Carbons of Cyclohexanones.

We describe a new synthetic reaction that generates all-carbon bis-quaternary centers at the opposing side of α-carbons in cyclohexanone with four different substituents in a controlled manner. Catalyzed by Cu(MeCN)4BF4 salt, this chemistry is proposed to proceed via an intermediacy of unsymmetrical O-allyl oxyallyl cations, which undergo a sequence of regioselective nucleophilic addition with substituted indoles and diastereoselective Claisen rearrangement in a single synthetic operation. The stereochemical outcome of the products features the cis diastereorelationship between the two aryl groups at the α,α'-positions.

Transition metal oxide nanoparticles as surfaces for surface-assisted laser desorption/ionization mass spectrometry of asphaltenes.

We report the first use of NiO, Fe3O4, TiO2, and Co3O4 nanoparticles as surfaces for surface-assisted laser desorption/ionization (SALDI) mass spectrometry of asphaltenes. Higher signal-to-noise ratios (S/Ns) for asphaltene species were observed using NiO and Fe3O4 nanoparticles for SALDI as compared to LDI, where both surfaces consistently provided 2- to 3-fold improved S/Ns. The new SALDI detection method showed reliable adsorption data measuring supernatant solutions after 24 hour asphaltene adsorption on NiO, Fe3O4, and Co3O4. These results indicated that NiO has a higher adsorption affinity than Fe3O4 and Co3O4 for asphaltene molecules, corroborating reported asphaltene adsorption on metal oxide nanoparticles.

Carbazole Annulation via Cascade Nucleophilic Addition-Cyclization Involving 2-(Silyloxy)pentadienyl Cation.

We report a new strategy toward the synthesis of highly functionalized carbazoles via 2-(silyloxy)pentadienyl cation intermediates, which were generated upon ionization of vinyl-substituted α-hydroxy silyl enol ethers under Brønsted acid catalysis. These electrophilic species were found to readily undergo cascade reactions with substituted indoles to generate carbazole molecular scaffolds in good yields via a sequence of regioselective nucleophilic addition, followed by intramolecular dehydrative cyclization.

Functionalization of Silyldienol Ethers at the γ-Position via 2-Silyloxypentadienyl Cations.

This report describes Brønsted acid catalyzed de novo synthesis of silyldienol ethers bearing tetrasubstituted double bonds via an intermediacy of 2-silyloxypentadienyl cations. The reactivity of these novel cationic intermediates could be modulated and harnessed toward direct nucleophilic additions regioselectively at the γ-position to produce highly functionalized silyldienol ethers with tunable control of the resulting double bond geometry.

An expedient synthesis of functionalized 1,4-diketone-derived compounds via silyloxyallyl cation intermediates.

Herein we describe a new method, enabling the synthesis of highly functionalized 1,4-diketones that are readily differentiated as monosilylenol ethers under Brønsted acid catalysis. This synthetically useful chemistry exploited an intermediacy of unsymmetrical silyloxyallyl cations, which were directly captured by silyl enolates to create the targeted α,α carbon-carbon linkages in a regioselective manner. Our reaction conditions proved to be mild, rendering the silylenol ether functionalities intact.

Cooperative benzylic-oxyallylic stabilized cations: regioselective construction of α-quaternary centers in ketone-derived compounds.

We describe a novel reactivity of benzylic-stabilized oxyallyl cations towards regioselective construction of carbon quaternary centers. These synthetically useful intermediates were readily generated upon ionization of aryl substituted α-hydroxy methylenol ethers with catalytic, mild Brønsted acid. The emerging unsymmetrical oxyallyl cations were then directly captured by indoles and other nucleophiles with exquisite control of regioselectivity, predictably at the electrophilic carbon bearing the alkyl substituent to produce highly functionalized, value-added enol ethers.

Tetra-kis(aceto-nitrile)copper(I) hydrogen oxalate-oxalic acid-aceto-nitrile (1/0.5/0.5).

In the title compound, [Cu(CH3CN)4](C2HO4)·0.5C2H2O4·0.5CH3CN, the Cu(I) ion is coordinated by the N atoms of four aceto-nitrile ligands in a slightly distorted tetra-hedral environment. The oxalic acid mol-ecule lies across an inversion center. The aceto-nitrile solvent mol-ecule is disordered across an inversion center and was refined with half occupancy. In the crystal, the hydrogen oxalate anions and oxalic acid mol-ecules are linked via O-H⋯O hydrogen bonds, forming chains along [010].