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111.
The mechanism of the metalation of 2-biphenyl carboxylic acid (1) with the Lochmann-Schlosser superbase was determined by deuteriolysis. Both ortho (C(3)) and remote (C(2')) positions are metalated. The C(2')-metalated species 2 cyclizes instantaneously. Under suitable conditions, the doubly charged geminal dimetallo dialkoxide group C(OM)(2) 4 directs metalation in the adjacent position (C(1)), affording a stable 1-metallo-9H-fluorene-9,9-dimetallo dialkoxide 5 that can be trapped by diverse electrophiles to give 1-substituted 9H-fluoren-9-ones 7 and 9 after acidic workup. [structure: see text] 相似文献
112.
Prof. Dr. Santanu Bhattacharya Dr. Suman K. Samanta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(52):16632-16641
The synthesis, hydrogelation, and aggregation‐induced emission switching of the phenylenedivinylene bis‐N‐octyl pyridinium salt is described. Hydrogelation occurs as a consequence of π‐stacking, van der Waals, and electrostatic interactions that lead to a high gel melting temperature and significant mechanical properties at a very low weight percentage of the gelator. A morphology transition from fiber‐to‐coil‐to‐tube was observed depending on the concentration of the gelator. Variation in the added salt type, salt concentrations, or temperature profoundly influenced the order of aggregation of the gelator molecules in aqueous solution. Formation of a novel chromophore assembly in this way leads to an aggregation‐induced switch of the emission colors. The emission color switches from sky blue to white to orange depending upon the extent of aggregation through mere addition of external inorganic salts. Remarkably, the salt effect on the assembly of such cationic phenylenedivinylenes in water follow the behavior predicted from the well‐known Hofmeister effects. Mechanistic insights for these aggregation processes were obtained through the counterion exchange studies. The aggregation‐induced emission switching that leads to a room‐temperature white‐light emission from a single chromophore in a single solvent (water) is highly promising for optoelectronic applications. 相似文献
113.
Mesoporous silica supported ytterbium as catalyst for synthesis of 1,2‐disubstituted benzimidazoles and 2‐substituted benzimidazoles 下载免费PDF全文
The benzimidazole ring is an important pharmacophore in contemporary drug discovery. Thus, effort to identifying new compounds containing benzimidazole scaffolds have gained much attention in recent years. In the present study, MCM‐41 type mesoporous silica with large pore (l‐MSN) supported ytterbium was successfully prepared by wet impregnation method. Among rare earth metal salts, ytterbium triflate has already been widely investigated as a catalyst in organic synthesis but less toxic ytterbium oxide has yet to be explored. Relatively high abundance and low cost of ytterbium with respect to many catalytically active metals (e.g. Pd, Au, Ru, Ir, Pt) offer an opportunity to develop sustainable catalysts for organic conversions. The catalyst has been characterized by various techniques including nitrogen adsorption, FT‐IR, TEM, SEM, EDX technique and elemental mapping. The obtained materials exhibit high surface area and a narrow distribution of mesoporosity. The catalytic performance of the Yb@l–MSNs was tested by synthesis of 1,2‐disubstituted benzimidazoles and 2‐substituted benzimidazoles through the coupling of aldehydes with o‐phenylenediamine. The catalyst resulted in excellent yields in short reaction times and the reaction showed tolerance toward both electron‐donating and electron‐withdrawing functional groups at room temperature. A particularly interesting finding was the solvent selectivity of this reaction; namely, 1,2‐disubstituted benzimidazoles generated as major product in water‐ethanol, while the 2‐substituted benzimidazoles was generated exclusively in non‐polar solvents like toluene. 相似文献
114.
Weiwei Yang Dr. Kushal Samanta Xintong Wan Dr. Tushar Ulhas Thikekar Yang Chao Shunshun Li Ke Du Dr. Jun Xu Yan Gao Prof. Han Zuilhof Prof. Andrew C.-H. Sue 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):4023-4028
Tiara[5]arenes (T[5]s), a new class of five-fold symmetric oligophenolic macrocycles that are not accessible from the addition of formaldehyde to phenol, were synthesized for the first time. These pillar[5]arene-derived structures display both unique conformational freedom, differing from that of pillararenes, with a rich blend of solid-state conformations and excellent host–guest interactions in solution. Finally we show how this novel macrocyclic scaffold can be functionalized in a variety of ways and used as functional crystalline materials to distinguish uniquely between benzene and cyclohexane. 相似文献
115.
116.
Studies of some quaternary compounds showing lattice matching condition on various substrates suitable for device design in
various wavelength regions have been reported here. The compositional dependence of lowest energy band gap, dielectric constant,
coefficient of thermal expansion, temperature and pressure dependence of lowest band gap energy, etc. of these compounds have been presented and finally proper concentrations suitable for device design under lattice matching
condition have been mentioned. 相似文献
117.
Bulk viscous fluid distribution with massive strings in LRS Bianchi type-1 space time is studied. The exact solutions of the
field equations are obtained by using the equation of state ρ=−λ and ρ=λ. We observed that the bulk viscous fluid does not survive for ρ=−λ whereas it survives for ρ=λ. Some physical and geometrical properties of the models are discussed. 相似文献
118.
Sk. Sheriff Shah Maniklal Shee Yarra Venkatesh Amit Kumar Singh Samya Samanta Prof. N. D. Pradeep Singh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3703-3708
The combination of an organic photocatalyst [4CzIPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6 dicyanobenzene) or 5MeOCzBN (2,3,4,5,6-pentakis(3,6-dimethoxy-9 H-carbazol-9-yl)benzonitrile)], quinuclidine, and tetra-n-butylammonium phosphate (hydrogen-bonding catalyst) was employed for amide bond formations. The hydrogen-bonded OH group activated the adjacent C−H bond of alcohols towards hydrogen atom transfer (HAT) by a radical species. The quinuclidinium radical cation, generated through single-electron oxidation of quinuclidine by the photocatalyst, employed to abstract a hydrogen atom from the α-C−H bond of alcohols selectively due to a polarity effect-produced α-hydroxyalkyl radical, which subsequently converted to the corresponding aldehyde under aerobic conditions. Then the coupling of the aldehyde and an amine formed a hemiaminal intermediate that upon photocatalytic oxidation produced the amide. 相似文献
119.
Annals of Operations Research - 相似文献
120.
Aniruddha Biswas Souradip Sarkar Dr. Rajarshi Samanta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3000-3004
An efficient pot-economic and step-economic RhIII-catalyzed site-selective direct amination/annulation strategy was developed for the synthesis of benzophenanthroline derivatives using quinoline N-oxides and anthranils. The method was further extended to the synthesis of nitrogen-containing extended π-conjugated benzophenanthrolinone derivatives. Late-stage functionalizations of cinchonidine and cinchophen derivatives and synthesis of a bioactive quinolino-indole were achieved. 相似文献