Project description:TiO2-supported PdAu bimetallic nanoparticles (NPs) with small size and good dispersity were prepared by the room-temperature ionic liquid-assisted bimetal sputtering, which is simple, environmentally friendly, and free of additives and byproducts. Pd/Au atomic ratio can be tuned by controlling the sputtering conditions simply. High catalytic activity was found in PdAu-NPs-TiO2 hybrids for solvent-free selective oxidation of 1-phenylethanol using O2 as the oxidant at the low temperature of 50 °C and low pressure of 1 atm. It was found that Pd/Au ratio strongly affected the catalytical activity, and the highest conversion of about 35 % and turnover frequency of about 421 h-1 were achieved at 1:1 of Pd/Au atomic ratio. The synergistic effect in PdAu NPs was also discussed based on the comprehensive characterization results. The present approach may offer an alternative platform for future development of green-chemistry compatible bimetallic nanocatalysts.
Project description:[reaction: see text] We report the catalytic asymmetric allylation of ketones under highly concentrated reaction conditions with a catalyst generated from titanium tetraisopropoxide and BINOL (1:2 ratio) in the presence of isopropanol. This catalyst promotes the addition of tetraallylstannane to a variety of ketones to produce tertiary homoallylic alcohols in excellent yield (80-99%) with high enantioselectivities (79-95%). The resulting homoallylic alcohols can also be epoxidized in situ using tert-butyl hydroperoxide (TBHP) to afford cyclic epoxy alcohols in high yield (84-87%).
Project description:By varying the steric and electronic surroundings of the hydrogen-bonding motif, the novel chiral Cinchona-alkaloid based selenoureas were developed. Acting as bifunctional catalysts, they were applied in the Michael reactions of dithiomalonate and nitrostyrene providing chiral adducts with up to 96% ee. The asymmetric Michael--hemiacetalization reaction of benzylidene pyruvate and dimedone, performed with the assistance of 5 mol% of selenoureas, furnished the product with up to 93% ee and excellent yields. The effectiveness of the new hydrogen-bond donors was also proved in solvent-free reactions under ball mill conditions, supporting the sustainability of the devised catalytic protocol.
Project description:Despite the proven value in utilizing pyrone dienes to create molecular complexity via Diels-Alder reactions with varied dienophiles, few examples of effective catalytic, asymmetric variants of this process have been developed. Herein, we show that the use of Jørgensen-Hayashi-type catalysts can convert an array of α,β-unsaturated aldehydes into chiral dienamines that can formally add in a Diels-Alder fashion to a number of electron-deficient pyrones of the coumalate-type to generate optically active [2.2.2]-bicyclic lactones. In most cases, the reactions proceed with good to excellent diastereo- and enantiocontrol (up to 99% ee). Models to explain that stereoselectivity, as well as several additional transformations of the resultant products, are also presented.
Project description:The development of new and greener approaches to organic synthesis has been a trend in recent years. Continuing the latest publications of our team, in this work, we demonstrate the efficiency of three solvents: eucalyptol (1,8-cineole), cyclopentyl methyl ether (CPME), and 2-methyltetrahydrofuran (2-MeTHF) for the synthesis of O,S,N-heterocyclic compounds.
Project description:High ionic carrier mobilities are important for the electrolyte solutions used in high-performance batteries. Based on the functional sharing concept, we fabricated mixed electrolytes consisting of solvate ionic liquids (SIL), which are highly concentrated solution electrolyte, and the non-coordinating low-viscosity dilution solvent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE). We investigated the thermal, transport, and static properties of electrolytes with different ratios of SIL to HFE. In particular, the interactions between the SILs and HFE and static correlations of the coordinating (ether-based molecules), non-coordinating (HFE), and carrier ionic species (lithium salt) were clarified by applying the excess density concept. Ether molecules always formed strong complexes with lithium cations regardless of the absence or presence of HFE. The repulsion force between the SILs and HFE was strongly affected by lithium salt concentration. From our results, we proposed dissociation/association models for these electrolyte systems.
Project description:An amine-triggered facile synthetic approach of anthranilates has been described through benzannulation of readily available chemicals under one-pot solvent-free conditions using Ca(OTf)2 as the sustainable catalyst. In this regioselective approach, we described a reasonably longer cascade, which proceeds through β-enamino ester formation/Michael addition/intramolecular aldol reaction/elimination/aromatization/oxidative debenzylation/lactonization with a broad substrate scope and high yields. The isolation of intermediates authenticated the mechanism, and the synthetic utility of the products was also demonstrated.
Project description:Rational solvent selection remains a significant challenge in process development. Here we describe a hybrid mechanistic-machine learning approach, geared towards automated process development workflow. A library of 459 solvents was used, for which 12 conventional molecular descriptors, two reaction-specific descriptors, and additional descriptors based on screening charge density, were calculated. Gaussian process surrogate models were trained on experimental data from a Rh(CO)2(acac)/Josiphos catalysed asymmetric hydrogenation of a chiral ?-? unsaturated ?-lactam. With two simultaneous objectives - high conversion and high diastereomeric excess - the multi-objective algorithm, trained on the initial dataset of 25 solvents, has identified solvents leading to better reaction outcomes. In addition to being a powerful design of experiments (DoE) methodology, the resulting Gaussian process surrogate model for conversion is, in statistical terms, predictive, with a cross-validation correlation coefficient of 0.84. After identifying promising solvents, the composition of solvent mixtures and optimal reaction temperature were found using a black-box Bayesian optimisation. We then demonstrated the application of a new genetic programming approach to select an appropriate machine learning model for a specific physical system, which should allow the transition of the overall process development workflow into the future robotic laboratories.
Project description:In this paper we report the first observation, through X-ray diffraction, of noncovalent uracil-uracil (U-U) dimeric π-stacking interactions in carbon nanotube (CNT)-based supramolecular assemblies. The directionally oriented morphology determined using atomic force microscopy revealed highly organized behavior through π-stacking of U moieties in a U-functionalized CNT derivative (CNT-U). We developed a dispersion system to investigate the bio-inspired interactions between an adenine (A)-terminated poly(3-adeninehexyl thiophene) (PAT) and CNT-U. These hybrid CNT-U/PAT materials interacted through π-stacking and multiple hydrogen bonding between the U moieties of CNT-U and the A moieties of PAT. Most importantly, the U···A multiple hydrogen bonding interactions between CNT-U and PAT enhanced the dispersion of CNT-U in a high-polarity solvent (DMSO). The morphology of these hybrids, determined using transmission electron microscopy, featured grape-like PAT bundles wrapped around the CNT-U surface; this tight connection was responsible for the enhanced dispersion of CNT-U in DMSO.
Project description:The iodination of pyrimidines is usually carried out by using toxic reagents under acidic conditions, such as with sulfuric acid and nitric acid. To avoid toxic reagents, we developed a simple and eco-friendly approach for the iodination of pyrimidine derivatives under solvent-free conditions using solid iodine and AgNO3 as an electrophilic iodinating reagent. The advantages of this method are the relatively short reaction time (20-30 min), simple set-up procedure, high yields (70-98%), and environmentally friendly reaction conditions. Our novel approach for the iodination of pyrimidines, as well as a variety of their derivatives, will contribute to the development of nucleobase-related drug candidates.