Eric Bosch

Synthesis of α-alkylidene-γ-lactones by intramolecular addition of alkoxycarbonyl free-radicals to acetylenes

Abstract α-Alkylidene-γ-lactones are obtained by treatment of chloroformate and selenocarbonate derivatives of homopropargylic alcohols with tri-n-butylstannane.

Selective nitration versus oxidative dealkylation of hydroquinone ethers with nitrogen dioxide

Abstract Various alkyl-substituted p-dialkoxybenzenes (ArH) react readily with nitrogen dioxide (NO2) in dichloromethane solution via either nitration (ArNO2) or oxidative dealkylation to quinones (Q). Spectral transients indicate that these coupled processes from the dialkoxybenzene radical cation (ArH+·) formed as the common reactive intermediate from electron-transfer in the disproprtionated precursor [ArH, NO+] N03−. In fast subsequent steps. ArH+· undergoes homolytic coupling with NO2 (which leads to aromatic nitration) and nucleophilic attack of NO3− (which results in oxidative dealkylation). As such, the competition between nitration and oxidative dealkylation is effectively modulated by solvent polarity and added nitrate.

Convenient preparation of quinones via the catalytic autoxidation of hydroquinones with nitrogen oxides

Abstract An efficient, inexpensive, catalytic method for the autoxidation of hydroquinones utilizes the gaseous (NO x ) catalyst which allows a simple workup procedure for quinone isolation merely by solvent removal.

Cation-Induced π-Stacking

The design and synthesis of a new dipyridyl ligand with appended phenanthryl moieties is described. On addition of increments of silver(I) trifluoromethanesulfonate to a solution of the ligand, the phenanthryl protons shift upfield in the (1)H NMR spectrum, suggesting that the phenanthrenes pi-stack on coordination of silver(I). In accord with this, the oxidation potential decreased from 1.74 to 1.55 V on complexation of silver(I). The pi-stacking was confirmed with the single-crystal X-ray structure of a palladium(II) coordination complex.

Crystal structure of kinetic and thermodynamic coordination networks formed between 3,3′-dipyridylethyne and copper bromide

Reaction of copper(I) bromide with 3,3′-dipyridylethyne yielded rhomboid yellow crystals that are stable when removed from the mother liquor. X-Ray crystallographic analysis identified the one-dimensional coordination polymer formed with pairs of dipyridyl ligands bridging rhombic CuBr2Cu units. The crystals left in the mother liquor re-dissolved and formed orange hexagonal prisms that were shown to be a stable three-dimensional network comprising interwoven ligand–copper ribbons linked together by infinite copper–bromide chains.

Desilylation of α-trimethylsilylmethylene-δ-lactones. A new route to α-methylene-δ-lactones

Abstract Addition of phenylthiol to α-trimethylsilylmethylene-δ-lactones affords α-phenylthi(trimethylsilyl)methyl-δ-lactones which, on treatment with tetrabutyl-ammonium fluoride and methyl acrylate give the corresponding α-methylene-δ-lactones through a one-pot double deblocking process.

Intramolecular Halogen Bonding Supported by an Aryldiyne Linker

Intramolecular halogen bonds between aryl halide donors and suitable acceptors, such as carbonyl or quinolinyl groups, held in proximity by 1,2-aryldiyne linkers, provide triangular structures in the solid state. Aryldiyne linkers provide a nearly ideal template for intramolecular halogen bonding as minor deviations from alkyne linearity can accommodate a variety of halogen bonding interactions, including O···Cl, O···Br, O···I, N···Br, and N···I. Halogen bond lengths for these units, observed by single crystal X-ray crystallography, range from 2.75 to 2.97 Å. Internal bond angles of the semirigid bridge between halogen bond donor and acceptor are responsive to changes in the identity of the halogen, the identity of the acceptor, and the electronic environment around the halogen, with the triangles retaining almost perfect co-planarity in even the most strained systems. Consistency between experimental results and structures predicted by M06-2X/6-31G* calculations demonstrates the efficacy of this computational method for modeling halogen-bonded structures of this type.

Chain-link hydrogen-bonded capsules

An approach to the design, synthesis and characterization of chain-link hydrogen-bonded capsules is described. The process involves the self-assembly of a series of bipyrimidines, namely 5,5′-bipyrimidine, 1,2-bis(5′pyrimidyl)ethyne and 1,2-bis(5′pyrimidyl)ethene with C-methyl calix[4]resorcinarene. The structures of resultant chain-link hydrogen-bonded capsules are presented.

Preparation of 2′-aminoacetophenones: a one-pot hydration and reduction of 1-ethynyl-2-nitrobenzenes

Abstract The reductive hydration of 1-ethynyl-2-nitrobenzenes to the corresponding 2′-aminoacetophenones with a range of common reducing agents is described.

Spontaneous disproportionation of NO2 (N2o4) by aromatic hydrocarbons. Formation of nitrosonium EDA complexes as chemical intermediates

Strong (orange/red) colourations resulting immediately upon the exposure of nitrogen dioxide and its equilibrium dimer (dinitrogen tetroxide) to various aromatic hydrocarbons (ArH) are shown to arise from the nitrosonium EDA or electron donor-acceptor complexes [ArH, NO+NO3−]. The latter exhibit diagnostic charge-transfer absorptions and characteristic N-O stretching bands in the UV-vis and IR spectra, respectively, that relate directly to ArH/NO+ interactions extant in the EDA complexes previously derived from the authentic nitrosonium salt, NO+PF6-. Time-resolved picosecond spectroscopy establishes the charge-transfer excited state of [ArH, NO+NO3−] to be essentially identical to that from [ArH, NO+BF4−]. Furthermore, the same temporal decay of the spectral transients (ArH+•) from both systems indicates minimal ion-pairing effects of the counterions (NO3− and BF4−) on the kinetics of back electron transfer.