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1.
Polyethylene glycol (PEG) is found to be an inexpensive, nontoxic, environmentally friendly reaction medium for the conjugate addition of thiols to conjugated alkenes to afford the corresponding adducts in excellent yields under mild and neutral conditions. Products of undesirable side reactions resulting from polymerization are not observed. The use of PEG avoids the use of either acid or base catalysts for this conversion and moreover PEG can be recovered and reused. 相似文献
2.
Catalytic chain transfer polymerization of isobutylene: The role of nucleophilic impurities 下载免费PDF全文
Tota Rajasekhar Ujjal Haldar Jack Emert Philip Dimitrov Rich Severt Rudolf Faust 《Journal of polymer science. Part A, Polymer chemistry》2017,55(22):3697-3704
Fast polymerization of isobutylene (IB) initiated by tert‐butyl chloride using ethylaluminum dichloride·bis(2‐chloroethyl) ether complex (T. Rajasekhar, J. Emert, R. Faust, Polym. Chem. 2017, 8, 2852) was drastically slowed down in the presence of impurities, such as propionic acid, acetone, methanol, and acetonitrile. The effect of impurities on the polymerization rate was neutralized by using two different approaches. First, addition of a small amount of iron trichloride (FeCl3) scavenged the impurity and formed an insoluble · impurity complex in hexanes. The polymerization rate and exo‐olefin content were virtually identical to that obtained in the absence of impurities. Heterogeneous phase scavenger (FeCl3) exhibited better performance than homogenous phase scavengers. In the second approach, conducting the polymerization in wet hexanes, the fast polymerization of IB was retained in the presence of impurities with a slight decrease in exo‐olefin content. 1H NMR studies suggest that nucleophilic impurities are protonated in the presence of water, and thereby neutralized. Mechanistic studies suggest that the rate constant of activation (ka), rate constant of propagation (kp), and rate constant of β‐proton elimination (ktr) are not affected by the presence of impurities. To account for the retardation of polymerization in the presence of impurities, delay of proton transfer to monomer in the chain transfer step is proposed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3697–3704 相似文献
3.
A facile and selective oxidation of sulfides to sulfoxides using an L‐proline–H2O2 system for structurally divergent sulfide substrates with excellent yields at ambient conditions is reported. 相似文献
4.
Yadav M Rao R Kurani H Rathod J Patel R Singhal P Shrivastav PS 《Journal of chromatographic science》2010,48(10):811-818
A sensitive and high throughput ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS-MS) method has been developed for the determination of pramipexole, a dopamine agonist, in human plasma. Sample preparation involved liquid-liquid extraction of pramipexole and ranitidine as the internal standard (IS) in ethyl acetate from 100 μL human plasma. The chromatographic separation is achieved on a Waters Acquity UPLC BEH C18 (100 mm × 2.1 mm, 1.7 μm) analytical column using an isocratic mobile phase, consisting of 10 mM ammonium formate (pH 7.50)-acetonitrile (15:85, v/v), at a flow-rate of 0.5 mL/min. The precursor → product ion transition for pramipexole (m/z 212.1 → 153.0) and IS (m/z 315.0 → 176.1) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and positive ion mode. The method was validated over a wide dynamic concentration range of 20-4020 pg/mL. Matrix effect is assessed by post-column infusion experiment and the process efficiency were 91.9% and 85.7% for pramipexole and IS, respectively. The method is rugged and rapid with a total run time of 1.5 min and is applied to a bioequivalence study of 0.25 mg PPX tablet formulation in 30 healthy Indian male subjects under fasting condition. 相似文献
5.
Chandrashekar Ramarao Ramadevi Nandipati Rajasekhar Navakoti Ramanjaneyulu Kottamasu 《Tetrahedron letters》2012,53(6):637-640
1,2-Dihydroxy benzenes have been protected as cyclic diacetals using 2,3-butane dione. These diacetals are extremely robust and can be further chemically diversified and resolved with chirality embedded in the 1,4-dioxane ring attached to the aromatic back bone as a result of the anomeric effect. These systems can serve as ligands, auxiliaries or organocatalysts for asymmetric synthesis. 相似文献
6.
Surendra V. Singh Jayaram Vishakantaiah Jaya K. Meka Vijayan Sivaprahasam Vijayanand Chandrasekaran Rebecca Thombre Vijay Thiruvenkatam Ambresh Mallya Balabhadrapatruni N. Rajasekhar Mariyappan Muruganantham Akshay Datey Hugh Hill Anil Bhardwaj Gopalan Jagadeesh Kalidevapura P. J. Reddy Nigel J. Mason Bhalamurugan Sivaraman 《Molecules (Basel, Switzerland)》2020,25(23)
The building blocks of life, amino acids, are believed to have been synthesized in the extreme conditions that prevail in space, starting from simple molecules containing hydrogen, carbon, oxygen and nitrogen. However, the fate and role of amino acids when they are subjected to similar processes largely remain unexplored. Here we report, for the first time, that shock processed amino acids tend to form complex agglomerate structures. Such structures are formed on timescales of about 2 ms due to impact induced shock heating and subsequent cooling. This discovery suggests that the building blocks of life could have self-assembled not just on Earth but on other planetary bodies as a result of impact events. Our study also provides further experimental evidence for the ‘threads’ observed in meteorites being due to assemblages of (bio)molecules arising from impact-induced shocks. 相似文献
7.
Michelyne Haroun Santosh S. Chobe Rajasekhar Reddy Alavala Savita M. Mathure Risy Namratha Jamullamudi Charushila K. Nerkar Vijay Kumar Gugulothu Christophe Tratrat Mohammed Monirul Islam Katharigatta N. Venugopala Mohammed Habeebuddin Mallikarjun Telsang Nagaraja Sreeharsha Md. Khalid Anwer 《Molecules (Basel, Switzerland)》2022,27(12)
Considering the importance of benzothiazepine pharmacophore, an attempt was carried out to synthesize novel 1,5-benzothiazepine derivatives using polyethylene glycol-400 (PEG-400)-mediated pathways. Initially, different chalcones were synthesized and then subjected to a cyclization step with benzothiazepine in the presence of bleaching clay and PEG-400. PEG-400-mediated synthesis resulted in a yield of more than 95% in less than an hour of reaction time. Synthesized compounds 2a–2j were investigated for their in vitro cytotoxic activity. Moreover, the same compounds were subjected to systematic in silico screening for the identification of target proteins such as human adenosine kinase, glycogen synthase kinase-3β, and human mitogen-activated protein kinase 1. The compounds showed promising results in cytotoxicity assays; among the tested compounds, 2c showed the most potent cytotoxic activity in the liver cancer cell line Hep G-2, with an IC50 of 3.29 ± 0.15 µM, whereas the standard drug IC50 was 4.68 ± 0.17 µM. In the prostate cancer cell line DU-145, the compounds displayed IC50 ranges of 15.42 ± 0.16 to 41.34 ± 0.12 µM, while the standard drug had an IC50 of 21.96 ± 0.15 µM. In terms of structural insights, the halogenated phenyl substitution on the second position of benzothiazepine was found to significantly improve the biological activity. This characteristic feature is supported by the binding patterns on the selected target proteins in docking simulations. In this study, 1,5-benzothiazepines have been identified as potential anticancer agents which can be further exploited for the development of more potent derivatives. 相似文献
8.
Madhava Golla Subba Rao Devineni Rasheed Syed Bhanu Kiran Rayalacheru Rajasekhar Maram 《Phosphorus, sulfur, and silicon and the related elements》2017,192(7):794-798
The synthesis of a new series of P-heterocyclic compounds, substituted 2-aminomethyl-2-oxo-2λ5-perhydro-[1,3,2]oxazaphospholo[3,4-a]pyridine derivatives 8(a-j), was accomplished. A key intermediate, 2-(chloromethyl)-2-oxo-2λ5-perhydro-[1,3,2]oxazaphospholo[3,4-a]pyridine (6) was primarily synthesized by the condensation of (±)-2-piperidinemethanol (4) and chloromethylphosphonic dichloride (5); subsequently, it was treated with various heterocyclic amines/benzylamines/aminoacid esters, 7(a-j) to obtain the desired products. The structures of the newly synthesized compounds were elucidated by 1H, 13C, and 31P NMR spectroscopy, mass spectra and elemental analyses. The biological potency of title products was investigated by screening in vitro antimicrobial activity. The bio-screening data revealed that most of the synthesized derivatives showed potent growth of inhibition against fungi while compared with bacteria. Particularly, compounds 8c and 8i against bacterial strains, and 8a and 8f against fungi exhibited promising activity. 相似文献
9.
Rajasekhar V. S. R. Pullabhotla Colin Southway Sreekanth B. Jonnalagadda 《Reaction Kinetics and Catalysis Letters》2008,94(2):289-299
Photolysis behavior of acetamiprid in different kinds of surfactant solutions were investigated. The results showed that acetamiprid
was prone to photolysis when exposed to the irradiation of a mercury lamp, and the photolysis kinetics fit in well with the
first-order kinetic equation. Surfactants did not participate in the acetamiprid’s photolysis process directly, whereas they
all had obvious inhibiting effects on it. 相似文献
10.
[reaction: see text] The first organocatalytic cross aldol reaction of ketones and diethyl formylphosphonate hydrate has been realized by using readily available l-prolinamide as the catalyst. Secondary alpha-hydroxyphosphonates have been synthesized in high enantioselective (up to >99% ee) and good diastereoselectivity. 相似文献