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171.
Kaushik Sen Bhaskar Mondal Srimanta Pakhira Chandan Sahu Deepanwita Ghosh Abhijit K. Das 《Theoretical chemistry accounts》2013,132(8):1-17
The association reaction between silyl radical (SiH3) and H2O2 has been studied in detail using high-level composite ab initio CBS-QB3 and G4MP2 methods. The global hybrid meta-GGA M06 and M06-2X density functionals in conjunction with 6-311++G(d,p) basis set have also been applied. To understand the kinetics, variational transition-state theory calculation is performed on the first association step, and successive unimolecular reactions are subjected to Rice–Ramsperger–Kassel–Marcus calculations to predict the reaction rate constants and product branching ratios. The bimolecular rate constant for SiH3–H2O2 association in the temperature range 250–600 K, k(T) = 6.89 × 10?13 T ?0.163exp(?0.22/RT) cm3 molecule?1 s?1 agrees well with the current literature. The OH production channel, which was experimentally found to be a minor one, is confirmed by the rate constants and branching ratios. Also, the correlation between our theoretical work and experimental literature is established. The production of SiO via secondary reactions is calculated to be one of the major reaction channels from highly stabilized adducts. The H-loss pathway, i.e., SiH2(OH)2 + H, is the major decomposition channel followed by secondary dissociation leading to SiO. 相似文献
172.
We report a successful facile and novel approach for in situ synthesis of gold nanoparticles (AuNPs) via enzymatic dephosphorylation reaction at room temperature. Fmoc-tyrosine phosphate and cytidine-5-mono phosphate are used to sense the activities of an enzyme alkaline phosphatase. Formation of AuNps is highly selective towards biomolecules and it is readily detected colorimetrically and UV–Vis analysis. In this procedure, dephosphorylated product plays both roles as reducing and stabilizing agent to direct the formation of AuNPs in aqueous media. Transmission electron microscopic study reveales that hexagonal AuNPs were synthesized by using Fmoc-tyrosine phosphate and alkaline phosphatase. Wide angle X-ray scattering data confirms the formation of AuNPs. FT-IR studies confirm that biomolecules play crucial role to stabilize the AuNPs by molecular interactions with the surface of AuNPs. In situ synthesized AuNPs are applied for the sensing of enzyme activity. 相似文献
173.
Thermal [3,3] sigmatropic rearrangement of 6-cyclohex-2-enyloxy-1-methylquinolin-2(1H)-one (3) afforded 5-cyclohex-2-enyl-6-hydroxy-l-methyl-quinolin-2(1H)-one (4) in 86% yield. Compound 4 on treatment with pyridine hydrotribromide in CH2Cl2 gave exclusively non-bridged product 6 (85%) whereas compound 4 by a different route viz., acetylation followed by bromine addition and cyclization gave the bicyclic product 7 (80%). Compound 4 also furnished a bicyclic product 11 (80%) on treatment with cone. H2SO4. 相似文献
174.
Short and convenient synthesis of bicyclic lactones (1) and (2), important intermediates in trichothecene synthesis is described. 相似文献
175.
ZrOCl2 · 8H2O catalyzes the one-pot synthesis of β′-acetamido-β-dicarbonyl compounds in high yields from aldehyde, enolizable β-dicarbonyl compound, acetyl chloride, and acetonitrile in solvent as well as in solvent-free conditions. β′-Acetamido-β-ketoesters are formed in moderate to exclusive pref-diastereoselectivity. 相似文献
176.
Sitaram Pal Sukumar Ghosh Bimal K. Banik Shaikh Khairul Alam Usha Ranjan Ghatak 《合成通讯》2013,43(14):2203-2216
The bridged-ethers, (±)-2-methoxy-9a-carbamorphinan (1b) and (±)-2-methoxy-9a-carba-14α-morphinan(2b) have been synthesized. The acid-catalyzed cyclizations of 1-m-methoxy benzyloctalone 3b and 1-m-methoxybenzyloctalins 4b proceed with high regio-and stereoselectivities leading mostly to the bridged-ketone 14 and ether 1b respectively, along with o-methoxy-tetracyclic ketone 15 and the ether 17, in addition to other minor products. 相似文献
177.
4‐Mercaptothiocoumarin was alkylated with different propargylic and allylic halides under phase‐transfer‐catalyzed conditions in the presence of tetrabutylammonium bromide (TBAB) or benzyl triethylammonium chloride (BTEAC) catalyst in dichloromethane–aqueous NaOH solution (1%) at room temperature. These 4‐thiopropynyl and thioallyl thiocoumarins were then refluxed in chlorobenzene and quinoline to give thiopyrano[3,2‐c][1]benzothiopyran‐5(2H)‐one and thiopyrano[3,2‐c][1]benzothiopyran‐4‐one respectively. 相似文献
178.
Aasif Helal Hyun Gon Kim Manik Kumer Ghosh Cheol-Ho Choi Sung-Hong Kim Hong-Seok Kim 《Tetrahedron》2013
Two new reactive and highly selective turn-on fluorescent chemosensors based on the position of ring annulation of the naphthalene–thiazole moiety for aluminum ions in ethanol, were synthesized and investigated. It was found that sensors 2 and 4 exhibited a remarkable enhancement of emission upon complexation with Al3+. A TD-B3LYP/6-31G(d,p) calculation was performed to characterize the nature of the fluorescence behavior of sensors 2 and 4 upon Al3+ complexation. The mechanism of fluorescence was based on the cation promoted hydrolysis of ester and subsequent complexation. The combination of experimental and computational analyses provides a more complete understanding of the molecular level origin of these types of unique photophysical properties. 相似文献
179.
A series of polysubstituted pyrano[3,2-f]quinoline and phenanthroline derivatives have been synthesized by molecular iodine-catalyzed tandem reaction of various propargylic alcohols with or without substituted amines in excellent yields. Moreover, the cyclized side products are also pyrano[3,2-f]quinoline and phenanthroline derivatives. 相似文献
180.
Parnajyoti Karmakar Sumon Ray Debabrata Nandi Arup Mandal Subala Mondal Subhasis Mallick Biplab K. Bera Alak K. Ghosh 《Journal of solution chemistry》2013,42(2):441-458
The kinetics of the substitution reactions of [Pt(dach)(H2O)2]2+ and [Pt(en)(H2O)2]2+ (where ‘dach’ and ‘en’ are cis-1,2-diaminocyclohexane and ethylenediamine, respectively) with excess N,N′-diethylthiourea have been studied in aqueous solution by UV–Vis spectrophotometry. The effect of different N–N spectator ligands on the reactivity of platinum(II) complexes was investigated by studying the water lability of the reactant complexes. The kinetic study has been substantiated by product isolation, IR, NMR and ESI-MS spectral analysis and DFT calculations. The reactions follow normal square-planar substitution mainly in an associative way. Rate parameters have been evaluated under different conditions. The substitution rates of the complexes studied can be tuned through the nature of the N–N chelates, which is important in the development of new active compounds for cancer therapy. 相似文献