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191.
Conjugate addition of indoles and thiols with a variety of electron-deficient olefins mediated by a catalytic amount of Bi(OTf)3 at ambient temperature to afford the corresponding Michael adducts in good to excellent yields with high selectivity is reported. 相似文献
192.
B.K. BettadaiahP. Srinivas 《Tetrahedron letters》2003,44(39):7257-7259
Tertiary, allylic and benzylic alcohols react with 3,4,6-tri-O-acetyl-d-glucal in dichloromethane at 25°C in the presence of ZnCl2 to afford the corresponding 2,3-unsaturated-1-O-glucopyranoside acetates in 65-91% yields, with selective formation of the α-anomer. 相似文献
193.
Arene and phenylmethanesulfonyl chlorides can be cross-coupled with aryl, heteroaryl, and alkenylstannanes with desulfitation in the presence of 10 mol % CuBr.Me2S, 1.5 mol % Pd2dba3, and 5 mol % tri-2-furylphosphine in tetrahydrofuran or toluene under reflux. This extension of the Stille cross-coupling reaction realizes a new and economical method for the generation of C-C bonds. The palladium-catalyzed carbonylative Stille cross-coupling reactions of arenesulfonyl chlorides and organostannanes in the presence of CO (60 bar) at 110 degrees C in toluene generate the corresponding ketones. Arenesulfonyl chlorides are more reactive than aryl chlorides and aryl bromides in their Stille cross-coupling with organostannanes but less reactive than aryl iodides. The new methods disclosed for the generation of C-C bonds open new possibilities for medicinal chemistry and material sciences. 相似文献
194.
Rao RN Maurya PK Ramesh M Srinivas R Agwane SB 《Biomedical chromatography : BMC》2010,24(12):1356-1364
A high‐throughput liquid chromatography–electrospray ionization mass spectrometric (LC–ESI‐MS) method for screening of sirolimus on dried blood spots (DBS) was developed and validated. It involves solvent extraction of a punch of DBS followed by reversed‐phase LC on a relatively new monolithic column consisting of a silica rod with bimodal pore structure and detection by ESI‐MS. The run time was less than 3 min with a very low backpressure at a flow rate of 0.5 mL/min. The method can analyze more than 100 samples in an 8 h working day, including sample preparation. The assay was linear from 1 to 100 ng/mL. The mean recovery was 92.42%. The mean inter‐day and intra‐day precisions were 1.23 and 1.41%, respectively. The developed method is simple, rapid and useful for clinical applications. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
195.
Subash C. Jonnalagadda Steven R. Verga Parth D. Patel A. V. Reddy T. Srinivas Patricia M. Scott Venkatram R. Mereddy 《应用有机金属化学》2010,24(4):294-300
Novel synthetic protocols for the synthesis of lipophilic carboranes were developed utilizing two C? C bond forming reactions, namely Baylis–Hillman and enynedioate cycloaddition reactions. Some of these carboranes were converted into further functionalized carboranes via nucleophilic allylic isomerization. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
196.
2,3‐Dihydrothiophene 1,1‐dioxide (‘2‐sulfolene’) reacted with tosylmethyl isocyanide (TsMIC) in the presence of a base to give the hitherto unknown 3,5‐dihydro‐2H‐thieno[2,3‐c]pyrrole 1,1‐dioxide (‘β′‐sulfolenopyrrole’) from the expected cyclocondensation. A serendipitous formation of this β′‐sulfolenopyrrole was found earlier, when we investigated synthetic routes to a 3,5‐dihydro‐1H‐thieno[3,4‐c]pyrrole 2,2‐dioxide (a ‘β″‐sulfolenopyrrole’) from TsMIC and 2,5‐dihydrothiophene 1,1‐dioxide (‘3‐sulfolene’). Here, we present the synthesis and characterization of β′‐sulfolenopyrrole. The X‐ray crystal‐structure analyses of β′‐sulfolenopyrrole and the isomeric β″‐sulfolenopyrrole are also reported here. This β′‐sulfolenopyrrole is a new type of a functionalized pyrrole, which is likely to be of interest for pharmaceutical purposes. 相似文献
197.
198.
Dragulescu-Andrasi A Rapireddy S Frezza BM Gayathri C Gil RR Ly DH 《Journal of the American Chemical Society》2006,128(31):10258-10267
Peptide nucleic acid (PNA) is a synthetic analogue of DNA and RNA, developed more than a decade ago in which the naturally occurring sugar phosphate backbone has been replaced by the N-(2-aminoethyl) glycine units. Unlike DNA or RNA in the unhybridized state (single strand) which can adopt a helical structure through base-stacking, although highly flexible, PNA does not have a well-defined conformational folding in solution. Herein, we show that a simple backbone modification at the gamma-position of the N-(2-aminoethyl) glycine unit can transform a randomly folded PNA into a helical structure. Spectroscopic studies showed that helical induction occurs in the C- to N-terminal direction and is sterically driven. This finding has important implication not only on the future design of nucleic acid mimics but also on the design of novel materials, where molecular organization and efficient electronic coupling are desired. 相似文献
199.
K. Srinivas Sanyasi Sitha B. Sridhar V. Jayathirtha Rao K. Bhanuprakash K. Ravikumar 《Structural chemistry》2006,17(6):561-568
In order to study the keto and enol forms of cyanuric acid derivatives in the solid state, we have synthesized bis(2,4-benzyloxy)-6-(5H)-one-1,3,5-triazine, 1. Computational investigations indicate that keto form is more stable than enol form in both gas phase and solution phase
by 9.69–11.18 kcal mol−1 IR and crystallographic analysis shows that 1 exists in keto form in the solid state also. To obtain the enol form in the solid state, we adopted co-crystallization with
an organic base. The crystal structures of both keto/amine and the enol/imine forms (in a co-crystal) are reported.
IICT Communication No. 2505/CMM-0022. 相似文献
200.
Suzuki-Miyaura coupling reaction of N-protected 4-iodopheyl alanine isoxazoles with arylboronic acids, catalyzed by palladium, efficiently produce benzyl-N-(4-bipheyl)-2-(3-methyl-5(E)-2-aryl-1-ethenyl-4- isoxazolyl)-amino-2-oxoethyl) carba-mates in good yields. This process is first of its kind to construct carbon-carbon bond formation having biaryl motif on amino acid linked isoxazole moiety. 相似文献