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171.
A stereoselective method has been developed for the synthesis of (Z)- and (E)-allyl iodides from Baylis-Hillman adducts using polymethylhydrosiloxane (PMHS) and iodine in chloroform at room temperature. In addition, the reagent system has been utilized for the iodination of benzylic alcohols selectively. 相似文献
172.
Aggarwal S Ghosh NN Aneja R Joshi H Chandra R 《Rapid communications in mass spectrometry : RCM》2002,16(10):923-928
Positive ion mass spectral fragmentation of new N-carbamoyl/N-thiocarbamoyl derivatives of narcotine and compounds closely related to it are reported and discussed. The techniques used include electron impact (EI), fast-atom bombardment (FAB), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). Prominent peaks in the mass spectra of these compounds appear to involve C-C bond cleavage beta to the amine nitrogen with loss of the 4,5-dimethoxy(1H)isobenzofuranone moiety from their molecular ions, along with another prominent peak at m/z 382. No molecular ion peaks of these compounds were recorded in EI, whereas intense [M + H]+ ion peaks were observed in FAB and ESI spectra. MALDI also yielded [M + H]+ ion peaks in good agreement with FAB and ESI studies. 相似文献
173.
Biswanath Das Harish Holla Gurram Mahender Joydeep Banerjee Majjigapu Ravinder Reddy 《Tetrahedron letters》2004,45(39):7347-7350
Treatment of aldoximes with activated alkenes in the presence of diacetoxy iodobenzene (DIB) afforded isoxazolines in high yields. The method has been applied for the preparation of polyfunctional isoxazolines from Baylis-Hillman adducts. 相似文献
174.
Justin Y. Wang Kyoungmin Choi Stephan J. Zuend Kailaskumar Borate Harish Shinde Roland Goetz John F. Hartwig 《Angewandte Chemie (International ed. in English)》2021,60(1):399-408
Reported here is the Pd‐catalyzed C–N coupling of hydrazine with (hetero)aryl chlorides and bromides to form aryl hydrazines with catalyst loadings as low as 100 ppm of Pd and KOH as base. Mechanistic studies revealed two catalyst resting states: an arylpalladium(II) hydroxide and arylpalladium(II) chloride. These compounds are present in two interconnected catalytic cycles and react with hydrazine and base or hydrazine alone to give the product. The selectivity of the hydroxide complex with hydrazine to form aryl over diaryl hydrazine was lower than that of the chloride complex, as well as the catalytic reaction. In contrast, the selectivity of the chloride complex closely matched that of the catalytic reaction, indicating that the aryl hydrazine is derived from this complex. Kinetic studies showed that the coupling process occurs by rate‐limiting deprotonation of a hydrazine‐bound arylpalladium(II) chloride complex to give an arylpalladium(II) hydrazido complex. 相似文献
175.
Dr. Saroj Kumar Rout Dr. Agonist Kastrati Dr. Harish Jangra Dr. Kuno Schwärzer Dr. Alisa S. Sunagatullina Maximilien Garny Dr. Fabio Lima Dr. Cara E. Brocklehurst Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Hendrik Zipse Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(33):e202200733
DFT-calculations allow prediction of the reactivity of uncommon N-heterocyclic scaffolds of pyrazolo[1,5-a]pyrimidines and imidazo[1,2-b]pyridazines and considerably facilitate their functionalization. The derivatization of these N-heterocycles was realized using Grignard reagents for nucleophilic additions to 5-chloropyrazolo[1,5-a]pyrimidines and TMP2Zn ⋅ 2 MgCl2 ⋅ 2 LiCl allowed regioselective zincations. In the case of 6-chloroimidazo[1,2-b]pyridazine, bases such as TMP2Zn ⋅ MgCl2 ⋅ 2 LiCl, in the presence or absence of BF3 ⋅ OEt2, led to regioselective metalations at positions 3 or 8. Subsequent functionalizations were achieved with TMPMgCl ⋅ LiCl, producing various polysubstituted derivatives (up to penta-substitution). X-ray analysis confirmed the regioselectivity for key functional heterocycles. 相似文献
176.
177.
Detection and characterization of nonspecific,sparsely populated binding modes in the early stages of complexation
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Antonio Cardone Aaron Bornstein Harish C. Pant Mary Brady Ram Sriram Sergio A. Hassan 《Journal of computational chemistry》2015,36(13):983-995
A method is proposed to study protein–ligand binding in a system governed by specific and nonspecific interactions. Strong associations lead to narrow distributions in the proteins configuration space; weak and ultraweak associations lead instead to broader distributions, a manifestation of nonspecific, sparsely populated binding modes with multiple interfaces. The method is based on the notion that a discrete set of preferential first‐encounter modes are metastable states from which stable (prerelaxation) complexes at equilibrium evolve. The method can be used to explore alternative pathways of complexation with statistical significance and can be integrated into a general algorithm to study protein interaction networks. The method is applied to a peptide–protein complex. The peptide adopts several low‐population conformers and binds in a variety of modes with a broad range of affinities. The system is thus well suited to analyze general features of binding, including conformational selection, multiplicity of binding modes, and nonspecific interactions, and to illustrate how the method can be applied to study these problems systematically. The equilibrium distributions can be used to generate biasing functions for simulations of multiprotein systems from which bulk thermodynamic quantities can be calculated. © 2015 Wiley Periodicals, Inc. 相似文献
178.
Dongmei Wei Dan Meng Yuan Rong Yi Liu Harish Garg Dragan Pamucar 《Entropy (Basel, Switzerland)》2022,24(6)
The Fermatean fuzzy set (FFS) is a momentous generalization of a intuitionistic fuzzy set and a Pythagorean fuzzy set that can more accurately portray the complex vague information of elements and has stronger expert flexibility during decision analysis. The Combined Compromise Solution (CoCoSo) approach is a powerful decision-making technique to choose the ideal objective by fusing three aggregation strategies. In this paper, an integrated, multi-criteria group-decision-making (MCGDM) approach based on CoCoSo and FFS is used to assess green suppliers. To begin, several innovative operations of Fermatean fuzzy numbers based on Schweizer–Sklar norms are presented, and four aggregation operators utilizing the proposed operations are also developed. Several worthwhile properties of the advanced operations and operators are explored in detail. Next, a new Fermatean fuzzy entropy measure is propounded to determine the combined weight of criteria, in which the subjective and objective weights are computed by an improved best-and-worst method (BWM) and entropy weight approach, respectively. Furthermore, MCGDM based on CoCoSo and BWM-Entropy is brought forward and employed to sort diverse green suppliers. Lastly, the usefulness and effectiveness of the presented methodology is validated by comparison, and the stability of the developed MCGDM approach is shown by sensitivity analysis. The results shows that the introduced method is more stable during ranking of green suppliers, and the comparative results expound that the proposed method has higher universality and credibility than prior Fermatean fuzzy approaches. 相似文献
179.
Harish Bahadur 《Crystal Research and Technology》2006,41(7):631-635
This article presents a short review of impurity‐related point defects in crystalline quartz and their radiation induced modifications.In particular, a discussion has been presented on some of the prominent aluminum related alkali and proton compensated centers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
180.
Reshmi Thomas Sajesh P. Thomas Harish Lakhotiya Aref H. Mamakhel Martin Bondesgaard Victoria Birkedal Bo B. Iversen 《Chemical science》2021,12(37):12391
Alloy formation is ubiquitous in inorganic materials science, and it strongly depends on the similarity between the alloyed atoms. Since molecules have widely different shapes, sizes and bonding properties, it is highly challenging to make alloyed molecular crystals. Here we report the generation of homogenous molecular alloys of organic light emitting diode materials that leads to tuning in their bandgaps and fluorescence emission. Tris(8-hydroxyquinolinato)aluminium (Alq3) and its Ga, In and Cr analogues (Gaq3, Inq3, and Crq3) form homogeneous mixed crystal phases thereby resulting in binary, ternary and even quaternary molecular alloys. The MxM′(1−x)q3 alloy crystals are investigated using X-ray diffraction, energy dispersive X-ray spectroscopy and Raman spectroscopy on single crystal samples, and photoluminescence properties are measured on the exact same single crystal specimens. The different series of alloys exhibit distinct trends in their optical bandgaps compared with their parent crystals. In the AlxGa(1−x)q3 alloys the emission wavelengths lie in between those of the parent crystals, while the AlxIn(1−x)q3 and GaxIn(1−x)q3 alloys have red shifts. Intriguingly, efficient fluorescence quenching is observed for the MxCr(1−x)q3 alloys (M = Al, Ga) revealing the effect of paramagnetic molecular doping, and corroborating the molecular scale phase homogeneity.Multicomponent molecular alloy crystals exhibit intriguing effects of tuning and quenching in their photoluminescence, suggesting ‘alloy-crystal engineering’ as a useful design strategy for molecular functional materials. 相似文献