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81.
82.
Molecular distribution of stoichiometric copolycondensate trimethylolpropane/azelaïc acid with conversion is investigated. Weight fractions of the first oligomers determined by G.P.C. agree with theoretical forecasts. 相似文献
83.
Mironov M Gusev V Auregan Y Lotton P Bruneau M Piatakov P 《The Journal of the Acoustical Society of America》2002,112(2):441-445
It is demonstrated that the differentially heated stack, the heart of all thermoacoustic devices, provides a source of streaming additional to those associated with Reynolds stresses in quasi-unidirectional gas flow. This source of streaming is related to temperature-induced asymmetry in the generation of vortices and turbulence near the stack ends. The asymmetry of the hydrodynamic effects in an otherwise geometrically symmetric stack is due to the temperature difference between stack ends. The proposed mechanism of streaming excitation in annular thermoacoustic devices operates even in the absence of thermo-viscous interaction of sound waves with resonator walls. 相似文献
84.
Stereoretentive Palladium‐Catalyzed Arylation,Alkenylation, and Alkynylation of 1‐Thiosugars and Thiols Using Aminobiphenyl Palladacycle Precatalyst at Room Temperature 下载免费PDF全文
Alexandre Bruneau Dr. Maxime Roche Dr. Abdallah Hamze Dr. Jean‐Daniel Brion Dr. Mouad Alami Dr. Samir Messaoudi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8375-8379
A general and efficient protocol for the palladium‐catalyzed functionalization of mono‐ and polyglycosyl thiols by using the palladacycle precatalyst G3‐XantPhos was developed. The C?S bond‐forming reaction was achieved rapidly at room temperature with various functionalized (hetero)aryl‐, alkenyl‐, and alkynyl halides. The functional group tolerance on the electrophilic partner is typically high and anomer selectivities of thioglycosides are high in all cases studied. New sulfur nucleophiles such as thiophenols, alkythiols, and thioaminoacids (cysteine) were also successfully coupled to lead to the most general and practical method yet reported for the functionalization of thiols. 相似文献
85.
A systematic analysis of one-to-one chemical replacements occurring in a set of 50,000 druglike molecules was performed. The frequency of occurrence, as well as the average change in measured and calculated properties, was computed for each observed substitution. The experimental properties considered were solubility, protein binding, and logD. The calculated properties were logP, molecular weight, number of hydrogen bond donors and acceptors, and polar surface area. During this analysis, in which 9000 different functional groups were considered, 0.7 million substitutions were identified and stored in a database. As an application, we present a web interface from which users can identify historically observed replacements of any functional group on their query molecule. The server returns a list of side-chains, as well as the historically observed shift in experimental properties. 相似文献
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Three long-chain unsaturated esters (1-3), a fatty acid (4), a fatty ester (5), phytone (6) and a phloroglucinol (hyperfoliatin) (7) were isolated from the light petroleum extract of the endemic species Hypericum tomentosum L. (Clusiaceae). Compound 2, 8,10,13-trimethyltetradecanoic acid (2E)-3-methylhexadec-2-enyl ester, which we named tomentosate, is reported for the first time. The structures of the identified compounds were established on the basis of physical and spectroscopic analysis, and by comparison with literature data. 相似文献
90.
The use of a temporary protection by a chloro group at C5 of pyrazoles allows the synthesis of the 4-arylated pyrazoles, which were previously inaccessible by palladium-catalyzed direct arylation, with complete regioselectivity and in high yields using in most cases as little as 0.5-0.1 mol % Pd(OAc)(2) as the catalyst with electron-deficient aryl bromides. Moreover, from 5-chloro-1,3-dimethylpyrazole, sequential catalytic C4 arylation, dechlorination, catalytic C5 arylation reactions allowed the synthesis of a 4,5-diarylated pyrazole derivative. 相似文献