Exploration of transition-metal-catalyzed direct C-H arylation of nitro-substituted heteroarenes and further transformations of nitro group

The present work aimed to study the transition-metal-catalyzed direct C-H arylation of various nitro-substituted heteroarenes, including 4-nitroimidazole derivatives, 4-nitropyrazole derivatives, fused 3-nitropyridines, nitro-substituted pyrrole and thiophene. Under optimized reaction conditions a wide range of coupling partners were perfectly tolerated. Additional empirical studies indicated that the nitro group has influence on the regioselectivity of the reactions. In addition, the multipurpose nature of nitro group as a versatile directing group was explored

Improved Buchwald–Hartwig Amination by the Use of Lipids and Lipid Impurities

The development of green Buchwald–Hartwig aminations has long been considered challenging, due to the high sensitivity of the reaction to the environment. Here we show that food-grade and waste vegetable oils, triglycerides originating from animals, and natural waxes can serve as excellent green solvents for Buchwald–Hartwig amination. We further demonstrate that amphiphiles and trace ingredients present in triglycerides as additives have a decisive effect on the yields of Buchwald–Hartwig aminations

Renewable Solvents for Palladium-Catalyzed Carbonylation Reactions

Solvents constitute the largest component for many chemical processes and substitution of nonrenewable solvents is a longstanding goal for green chemistry. Here, we show that Pd-catalyzed carbonylative couplings, such as carbonylative cross-couplings, aminocarbonylations, and alkoxycarbonylations, can be successfully realized using renewable solvents. The present research covers not only well-established renewable solvents, such as 2-methyltetrahydrofuran (2MeTHF), limonene, and dimethyl carbonate, but also recently introduced biomass-derived 1,1-diethoxyethane, isosorbide dimethyl ether, eucalyptol, rose oxide, γ-terpinene, and α-pinene. The carbonylative coupling of boronic acids and aryl bromides works well in limonene. Aminocarbonylation gave excellent results in dimethyl carbonate, α-pinene, and limonene, while alkoxycarbonylation was successful in 2MeTHF, α-pinene, γ-terpinene, and dimethyl carbonate. The developed methods based on renewable solvents can be used for the synthesis of commercial drug Trimetozine and an analogue of Itopride

Bulky, electron-rich, renewable: analogues of Beller's phosphine for cross-couplings

In recent years, considerable progress has been made in the conversion of biomass into renewable chemicals, yet the range of value-added products that can be formed from biomass remains relatively small. Herein, we demonstrate that molecules available from biomass serve as viable starting materials for the synthesis of phosphine ligands, which can be used in homogeneous catalysis. Specifically, we prepared renewable analogues of Beller's ligand (di(1-adamantyl)-n-butylphosphine, cataCXium® A), which is widely used in homogeneous catalysis. Our new renewable phosphine ligands facilitate Pd-catalysed Suzuki– Miyaura, Stille, and Buchwald–Hartwig coupling reactions with high yields, and our catalytic results can be rationalized based on the stereoelectronic properties of the ligands. The new phosphine ligands generate catalytic systems that can be applied for the late-stage functionalization of commercial drugs

Onset of Optical Instabilities in the Nonlinear Optical Transmission of Heliconical Cholesteric Liquid Crystals

We report the result of an accurate calculation of optical transmission of a light beam traveling along the helix direction of a heliconical cholesteric liquid crystal when the light intensity is affecting the director orientation by an effective optical torque. The study is based on the application of Ambartsumian’s layer addition modified method with the aim of taking into account the continuous modification of the wave field during propagation, which is quite strong when the light wavelength approaches the Bragg resonance. We show first, that the recently calculated red shift of the transmission gap is confirmed under the constant intensity approximation. Additionally, by taking into account the full modulation of the optical field occurring at wavelengths close to the Bragg resonance, a weak red shift is already observable at very low intensities, but quickly has the onset of instabilities in the optical transmission. We give the first account of this effect, which is dependent on the light intensity showing and that it corresponds to the onset of non-uniform distribution of the conical angle and pitch of the structure

Light-Induced Self-Oscillations and Spoiling of the Bragg Resonance Due to Nonlinear Optical Propagation in Heliconical Cholesteric Liquid Crystals

In a recent paper, we have reported the results of a study of the nonlinear light propagation of a beam traveling along the helix direction of a heliconical cholesteric liquid crystal, showing that optical reorientation leads to instabilities in the optical transmission when the light wavelength is close to the Bragg resonance. Here we report a detailed study of this phenomenon, using Ambartsumian’s layer addition modified method to take into account the continuous modification of the wave field during propagation. We show that the whole transmission spectrum is modified by increasing the light intensity and point out that self-induced oscillations take place at lower intensities on the red side edge of the Bragg resonance while stable values of transmittivity are still observed on the blue side edge. A further increase in the intensity leads to oscillations of lower amplitude on the blue side while an irregular behavior of the transmission is achieved on the red side. At higher intensities, the Bragg resonance disappears and transmission becomes unstable for any light wavelength. A simple phenomenological model is proposed to account for the onset of the oscillations and the asymmetry of the behavior at the opposite side of the Bragg resonance. We also point out that the static electric field is a driving parameter to switch from stable to oscillatory to irregular behavior in the transmittivity at a given light wavelength