Photogeneration of Chlorine Radical from a Self-Assembled Fluorous 4CzIPN•Chloride Complex: Application in C-H Bond Functionalization.

The chlorine radical is a strong HAT (Hydrogen Atom Transfer) agent that is very useful for the functionalization of C(sp)-H bonds. Albeit highly attractive, its generation from the poorly oxidizable chloride ion mediated by an excited photoredox catalyst is a difficult task. We now report that 8R-4CzIPN, an electron-deficient fluorous derivative of the benchmark 4CzIPN photoredox catalyst belonging to the donor-acceptor carbazole-cyanoarene family, is not only a better photooxidant than 4CzIPN, but also becomes an excellent host for the chloride ion.

Singlet Oxygen Responsive Molecular Receptor to Modulate Atropisomerism and Cation Binding.

In switchable molecular recognition, O stimulus responsive receptors offer a unique structural change that is rarely exploited. The employed [4+2] reaction between O and anthracene derivatives is quantitative, reversible and easily implemented. To evaluate the full potential of this new stimulus, a non-macrocyclic anthracene-based host was designed for the modular binding of cations.

Chiral Anthranyl Trifluoromethyl Alcohols: Structures, Oxidative Dearomatization and Chiroptical Properties.

Chiral trifluoromethyl alcohol groups were introduced at the hindered ortho positions of 9,10-diphenylanthracenes to investigate their effects on the physical properties and reactivity towards oxidative dearomatization. In such compact structures, the position in different quadrants and the preferred orientation of the -CH(OH)CF groups were determined by the relative and absolute configurations of each stereoisomer, respectively. As a consequence, the stereochemistry governs the organization of the H-bonded molecules in single crystals (homochiral dimers vs ribbon), whereas in chlorinated solvents, they all behave as discrete compounds.

One-pot synthesis of isosorbide from cellulose or lignocellulosic biomass: a challenge?

The catalytic conversion of (ligno)cellulose is currently subject of intense research. Isosorbide is one of the interesting products that can be produced from (ligno)cellulose as it can be used for the synthesis of a wide range of pharmaceuticals, chemicals, and polymers. Isosorbide is obtained after the hydrolysis of cellulose to glucose, followed by the hydrogenation of glucose to sorbitol that is then dehydrated to isosorbide.

Chemo- and Regioselective Additions of Nucleophiles to Cyclic Carbonates for the Preparation of Self-Blowing Non-Isocyanate Polyurethane Foams.

Polyurethane (PU) foams are indisputably daily essential materials found in many applications, notably for comfort (for example, matrasses) or energy saving (for example, thermal insulation). Today, greener routes for their production are intensively searched for to avoid the use of toxic isocyanates. An easily scalable process for the simple construction of self-blown isocyanate-free PU foams by exploiting the organocatalyzed chemo- and regioselective additions of amines and thiols to easily accessible cyclic carbonates is described.

Singlet oxygen stimulus for switchable functional organic cages.

Molecular cages and incorporating a 9,10-diphenylanthracene (DPA) chromophore were synthesized through a templated ring-closure metathesis approach that allows variation in cavity size through the introduction of up to three different pillars. Reversible Diels-Alder reaction between the DPA moiety and photogenerated singlet oxygen smoothly converted and to the corresponding endoperoxide cages and , which are converted back to and upon heating. Endoperoxide formation constitutes a reversible covalent signal that combines structural changes in the interior of the cage with introduction of two additional coordination sites.

Experimental and theoretical investigation on the OH + CHC(O)CH reaction at interstellar temperatures (T=11.7-64.4 K).

The rate coefficient, (), for the gas-phase reaction between OH radicals and acetone CHC(O)CH, has been measured using the pulsed CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) technique ( = 11.7-64.4 K).

Organocatalytic Coupling of CO with a Propargylic Alcohol: A Comprehensive Mechanistic Study.

The metal-free coupling of a propargylic alcohol with CO catalysed by guanidine derivatives was investigated in detail through the combination of online kinetic studies by in situ attenuated-total reflection IR (ATR-IR) spectroscopy and DFT calculations. Bicyclic guanidines, namely 1,5,7-triazabicyclo[4.4.

Organocatalytic Coupling of CO with Oxetane.

The organocatalytic coupling of CO with oxetanes is investigated under solvent-free conditions. The influence of the main reaction parameters (type of organocatalytic system, pressure, and temperature) on the yield, the product formed, and the selectivity of the reaction are discussed. An onium salt combined with a fluorinated alcohol promotes the efficient and selective organocatalytic synthesis of α,ω-hydroxyl oligocarbonates by coupling CO with oxetanes at 130 °C and at a CO pressure as low as 2 MPa.

Quantum Tunneling Enhancement of the C + H2O and C + D2O Reactions at Low Temperature.

Recent studies of neutral gas-phase reactions characterized by barriers show that certain complex forming processes involving light atoms are enhanced by quantum mechanical tunneling at low temperature. Here, we performed kinetic experiments on the activated C((3)P) + H2O reaction, observing a surprising reactivity increase below 100 K, an effect that is only partially reproduced when water is replaced by its deuterated analogue. Product measurements of H- and D-atom formation allowed us to quantify the contribution of complex stabilization to the total rate while confirming the lower tunneling efficiency of deuterium.

Comparison of electron and chemical ionization modes for the quantification of thiols and oxidative compounds in white wines by gas chromatography-tandem mass spectrometry.

A rapid, sensitive method for assaying volatile impact compounds in white wine was developed using gas chromatography-tandem mass spectrometry (GC-MS/MS) technology, with a triple quadrupole analyzer operating in chemical ionization and electron impact mode. This GC-MS/MS method made it possible to assay volatile thiols (3SH: 3-sulfanylhexanol, formerly 3MH; 3SHA: 3-sulfanylhexyl acetate, formerly 3MHA; 4MSP: 4-methyl-4-sulfanylpentan-2-one, formerly 4MMP; BM: benzenemethanethiol; E2SA: ethyl 2-sulfanylacetate; and 2FM: 2-furanmethanethiol) and odoriferous oxidation markers (Sotolon: 4,5-dimethyl-3-hydroxy-2(5)H-furanone, methional, and phenylacetaldehyde) simultaneously in dry white wines, comparing electron impact (EI) and chemical ionization (CI) modes. More molecular ions were produced by CI than protonated molecules, despite the greater fragmentation caused by EI.

Fluorinated Alcohols as Activators for the Solvent-Free Chemical Fixation of Carbon Dioxide into Epoxides.

The addition of fluorinated alcohols to onium salts provides highly efficient organocatalysts for the chemical fixation of CO2 into epoxides under mild experimental conditions. The combination of online kinetic studies, NMR titrations and DFT calculations allows understanding this synergistic effect that provides an active organocatalyst for CO2 /epoxides coupling.

Charge dissociation at interfaces between discotic liquid crystals: the surprising role of column mismatch.

The semiconducting and self-assembling properties of columnar discotic liquid crystals have stimulated intense research toward their application in organic solar cells, although with a rather disappointing outcome to date in terms of efficiencies. These failures call for a rational strategy to choose those molecular design features (e.g.

Gas-phase kinetics of the hydroxyl radical reaction with allene: absolute rate measurements at low temperature, product determinations, and calculations.

The gas phase reaction of the hydroxyl radical with allene has been studied theoretically and experimentally in a continuous supersonic flow reactor over the range 50 ≤ T/K ≤ 224. This reaction has been found to exhibit a negative temperature dependence over the entire temperature range investigated, varying between (0.75 and 5.

Silylboranes as new sources of silyl radicals for chain-transfer reactions.

Various silylboranes, which were outfitted with a catecholborane moiety at one end and a (Me(3)Si)(3)Si moiety at the other end of a carbon chain, were prepared through the hydroboration of the corresponding unsaturated silanes. The C-centered radical species generated from these silylboranes efficiently cyclized to provide, through a 5-exo intramolecular homolytic substitution at the silicon center, the corresponding silacycle and a Me(3)Si radical that was subsequently trapped by sulfonyl acceptors. These cyclizations proceeded at unprecedented rates, due, in part, to a strong gem-dialkyl effect that was attributable to the presence of bulky substituents on a quaternary center located on the chain.

Allylsilanes in "tin-free" oximation, alkenylation, and allylation of alkyl halides.

Tin-free oximation, vinylation, and allylation of alkyl halides have been developed by using allylsilanes as di-tin surrogates. Initiation of the radical process with a peroxide provides the silyl radical, which can abstract a halogen from the corresponding alkyl halide. The resulting carbon-centered radical then adds to various acceptors, including a sulfonyloxime, a vinylsulfone, and an allylsulfone, leading to formation of the desired products along with the corresponding allylsulfone resulting from the reaction of the PhSO(2) radical with the allylsilane precursor.

On the interaction between supercritical CO2 and epoxides combining infrared absorption spectroscopy and quantum chemistry calculations.

The nature and strength of the interactions occurring between epoxides and CO(2) have been investigated by combining infrared spectroscopy with quantum chemistry calculations. A series of infrared absorption experiments on four model epoxide molecules highly diluted in supercritical CO(2) have been performed at constant temperature T = 40 °C for various CO(2) pressures varying from 1 to 30 MPa. Then, we carried out a theoretical analysis based on quantum chemistry calculations using Density Functional Theory (B3PW91 and CAM-B3LYP) and ab initio (MP2) computational methods.

Supramolecular organization and charge transport properties of self-assembled π-π stacks of perylene diimide dyes.

Molecular dynamics (MD) simulations have been coupled to valence bond/Hartree-Fock (VB/HF) quantum-chemical calculations to evaluate the impact of diagonal and off-diagonal disorder on charge carrier mobilities in self-assembled one-dimensional stacks of a perylene diimide (PDI) derivative. The relative distance and orientation of the PDI cores probed along the MD trajectories translate into fluctuations in site energies and transfer integrals that are calculated at the VB/HF level. The charge carrier mobilities, as obtained from time-of-flight numerical simulations, span several orders of magnitude depending on the relative time scales for charge versus molecular motion.

Gas-phase kinetics of hydroxyl radical reactions with C3H6 and C4H8: product branching ratios and OH addition site-specificity.

Products of the reaction of OH radicals with propene, trans-2-butene, and 1-butene have been investigated in a fast flow reactor, coupled with time-of-flight mass spectrometry, at pressures between 0.8 and 3.0 Torr.

Effect of the dynamical disorder on the second-order nonlinear optical responses of helicity-encoded polymer strands.

By combining classical samplings with quantum chemistry semiempirical time-dependent Hartree-Fock calculations, the high impact of dynamic fluctuations on the NLO properties of helical strands has been evidenced. In particular, these fluctuations are responsible for relative variations of approximately 20% in the hyper-Rayleigh responses in both pyridine-pyrimidine (py-pym) and hydrazone-pyrimidine (hy-pym) strands. Then, dynamical disorder has an even more important impact on the electric-field-induced second harmonic generation responses, whose variations can reach 2 (py-pym) or 5 (hy-pym) times their mean value.

Mechanistic aspects of the solid-state transformation of ammonium cyanate to urea at high pressure.

The chemical transformation of ammonium cyanate into urea has been of interest to many generations of scientists since its discovery by Friedrich Wöhler in 1828. Although widely studied both experimentally and theoretically, several mechanistic aspects of this reaction remain to be understood. In this paper, we apply computational methods to investigate the behavior of ammonium cyanate in the solid state under high pressure, employing a theoretical approach based on the self-consistent-charges density-functional tight-binding method (SCC-DFTB).