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1.
Dr. Takeshi Nanjo Natsuki Kato Xuan Zhang Prof. Yoshiji Takemoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(68):15504-15507
Strategies for the formation of amide bonds, that is, one of the most basic and important transformations in organic synthesis, have so far focused predominantly on dehydration reactions. Herein, we report and demonstrate the practical utility of a novel decarboxylative amidation of α-ketoacids by using inexpensive tert-butyl hydroperoxide (TBHP), which is characterized by high yields, a broad substrate scope, mild reaction conditions, and a unique chemoselectivity. These features enable the synthesis of peptides from amino acid derived α-ketoacids under preservation of the stereochemical information. 相似文献
2.
Jaedong Cho John Blackwell Sergei N. Chvalun Morton Litt Yuan Wang 《Journal of Polymer Science.Polymer Physics》2004,42(13):2576-2585
As‐cast films of poly(2,5‐benzimidazole) exhibit uniplanar orientation in which the planes of the aromatic rings lie parallel to the film surface. Upon doping with phosphoric acid, the original crystalline order is lost, but the doped film can be stretched to produce films with uniaxial orientation. After thermal annealing at 540 °C, nine Bragg reflections are resolved in the fiber diagram, and these are indexed by an orthorhombic unit cell with the dimensions a = 18.1 Å, b = 3.5 Å, and c = 11.4 Å, containing four monomer units of two chains. The absence of odd‐order 00l reflections points to a 21 chain conformation, which is probably planar so that the aromatic units can be stacked along the b axis. The water and phosphoric acid contents of the crystalline structure cannot be determined exactly because of the presence of extensive amorphous regions that probably have different solvation. The best agreement between the observed and calculated intensities is for an idealized structure containing two phosphoric acids and two water molecules per unit cell. However, the phosphoric acid is probably present mainly in the form of pyrophosphoric acid and its higher oligomers. In addition, the X‐ray data are consistent with a more disordered structure containing chains with random (up and down) polarity and a lack of c‐axis registry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2576–2585, 2004 相似文献
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Marina DellaGreca 《Tetrahedron》2006,62(12):2877-2882
Examination of the hydroalcoholic extract of the leaves of Aptenia cordifolia has afforded three cinnamic acid amides and two lignanamides. Structures were established on the basis of spectroscopic data, including 2D-NMR analyses. 相似文献
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A. S. Peregudov L. N. Usatova E. I. Smyslova E. I. Fedin D. N. Kravtsov 《Russian Chemical Bulletin》1995,44(8):1513-1519
It has been shown by the19F NMR method that the relative polarities of nitrogenelement bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and PPh3Au derivatives increase in the order N-H19F NMR. It has been found that these reactions occur by a bimolecular associative mechanism and that the N-H bond is substantially less reactive than the N-Hg and N-Au bonds, which have identical reactivities within the limits of sensitivity of the method used.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1574–1580, August, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 93-03-5528). 相似文献
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A. V. Tarasov P. O. Yablonsky Yu. A. Moskvichev 《Chemistry of Heterocyclic Compounds》2003,39(1):119-122
Various methods were studied for the oxidation of 2-methyl-5-(phenylsulfonyl)benzenesulfamide and its derivatives. The oxidation by sodium dichromate in sulfuric acid was found most efficient. The effects of temperature, concentration, reagent ratio, and time of the oxidation reaction on the yield of the desired product were investigated. Conditions were proposed for obtaining the desired product in yields up to 95%. A synthesis was developed for a series of new saccharin derivatives. 相似文献
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