查看更多>>摘要：A simple and convenient method for the esterification of various monosaccharide and disaccharide uronic acids, derived from glucose, galactose and mannose, was developed with different alcohols using the ecofriendly catalyst silica-sulphuric acid (H2SO4-SiO2). The esterification reactions proceeded at room temperature under mild conditions with excellent yields. Under the standard reaction conditions, various sensitive protecting groups, including acetyl, benzoyl, pivaloyl, isopropylidene, benzyl, naphthyl, etc., were well tolerated. Partially protected uronic acids underwent esterification without undergoing self condensation reactions. Published by Elsevier Ltd.
查看更多>>摘要：3-Chloro-2-oxo-N,3-diarylpropanamides, readily obtained from aromatic aldehydes and dichloroacetic acid anilides under Darzens condensation conditions or isomerization of 2-chloro-N,3-diaryloxirane-2carboxamides, proved to be excellent starting compounds for the synthesis 3-chloro(aryl)methyl)-3hydroxyindolin-2-ones with the formation of a new C(sp2)-C(sp2)- bond via intramolecular FriedelCrafts alkylation. Under optimized reaction conditions, the title compounds are obtained in a one-pot process, which involves a treatment of N-benzyl-3-chloro-2-oxo-N,3-diarylpropanamides with a CF3CO2H. The reactions proceed with the formation of easily separated by column chromatography anti and syn diastereomeric mixtures with a predominance of 36-49% of the formers. (c) 2022 Published by Elsevier Ltd.
查看更多>>摘要：Transition-metal-catalyzed annulation reactions of difluorocyclopropenes with alkynes or N,N-dialkylformamides and homocoupling reaction of difluorocyclopropenes have been realized under mild conditions. These reactions tolerate a range of functional groups, furnishing the corresponding products in moderate to good yields. In addition, isotope labeling experiment shows that water indeed involves in these reactions as an important component. (C) 2022 Published by Elsevier Ltd.
查看更多>>摘要：The reduction of benzylic, tertiary, and allylic alcohols with hydrosilane was efficiently catalyzed by the rhenium complex, such as ReBr(CO)5, to give the corresponding deoxygenarated products, alkanes, in moderate to good yields. In the case of aliphatic secondary alcohol, the alkane was formed along with the formation of dehydrated products. On the other hand, in the case of primary and cyclic alcohols, silylation of alcohols proceeded to form the corresponding silyl ethers.(c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：A facile, solvent-free, lower-cost, and efficient high-speed ball milling reaction catalyzed by Cu (NO3)2.3H2O/P2O5 is developed for the synthesis of symmetric ethers from dehydration of benzyl alcohols by taking a benzylic carbocation as intermediate.(c) 2022 Elsevier Ltd. All rights reserved.
Jackson, Amy C.Olsen, James T.Sundstrom, SashaLambert, Kyle M....
5页
查看更多>>摘要：A ring expansion of tetramic acids (pyrrolidine-2,4-diones) to N-oxy-2,5-diketopiperazines (DKPs) is described. This method allows for the facile and late-stage construction of the hydroxamic acid moiety and can thereby serve as a general method for accessing N-oxy-2,5-DKP natural products. (C) 2022 Elsevier Ltd. All rights reserved.
Suzuki, YuichiTaniguchi, KosukeHoang, Hai NamTamura, Mayumi...
5页
查看更多>>摘要：The investigation on the applicability of CO2 as a solvent has been increasingly important due to the need to develop efficient reactions replacing ordinary organic solvents derived from fossil fuel with sustainable solvents such as pressurized CO2. In our previous study of solvent engineering of a lipase-catalyzed reaction of bulky substrates, the conversions were higher for the reaction in CO2-expanded liquids, liquids expanded by dissolving pressurized CO2, than that in the liquids without CO2. This study demonstrates the detailed examination of CO2-expanded liquids as solvents for lipase-catalyzed kinetic resolution of racemic 1-tetralol, 2-tetralol, and substituted 1-tetralol analogs since chiral substituted tetralol analogs are important pharmaceutical intermediates. CO2-expanded liquids accelerated the reaction rate by up to 40 times of the reactions without CO2 while maintaining excellent enantioselectivities (E > 200). Preparative scale reactions of racemic 1-tetralol and 2-tetralol successfully gave the corresponding (R)-acetates and (S)-alcohols with high yields and excellent enantioselectivities (up to ee > 99%). (c) 2022 Elsevier Ltd. All rights reserved.
查看更多>>摘要：The facile construction of phenanthrene derivatives through the intermoletetradehydro-Diels-Alder (TDDA) reaction of benzyne in situ generated by the hexadehydro-Diels-Alder (HDDA) reaction with various substituted phenylacetylene was described. The naphthalene derivatives were obtained unexpectedly in another reaction modle when expanding substrate scope. The reaction profiles has good chemoselectivity and provided a new way for the synthesis of highly functionalized phenanthrene and naphthalene derivatives from simple materials under relatively mild conditions. (C) 2022 Elsevier Ltd. All rights reserved.
Bardasov, Ivan N.Alekseeva, Anastasiya U.Shishlikova, Maria A.V. Ershov, Oleg...
6页
查看更多>>摘要：The novel turn-on fluorescent chemosensors for silver ion based on nicotinonitriles, containing a tricyanobutadiene moiety (tricyanopyridine, TCPy) were developed. The enchantment of fluorescent emission can be observed by naked eye, even in the presence of interference cations. The binding mode turned out to be a 1: 1 ratio as determined using Job's plot. (c) 2022 Elsevier Ltd. All rights reserved.
Calabretta, Lindsey O.Thomas, Vienna M.Raines, Ronald T.
3页
查看更多>>摘要：Octanol-water partitioning experiments in the presence of carboxylate-, phosphate-, and sulfate -containing anionic lipids revealed that Ac-Cav-NH2 (where Cav refers to delta-oxa-arginine) partitions less into octanol than does Ac-Arg-NH2, suggesting that a cell-penetrating peptide based on canavanine would be relatively ineffective. (C) 2022 Published by Elsevier Ltd.
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