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991.
Synthesis of functionalized diaryl sulfides based on regioselective one-pot cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes 总被引:1,自引:0,他引:1
Functionalized diaryl sulfides were prepared based on one-pot cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes. 相似文献
992.
A concise process for the stereoselective synthesis of chiral cis-3-alkoxy-2-carbomethoxy medium-ring oxacycles from (R)-3-(3-butenyl)-4-propynoyloxazolidin-2-one (1) was developed. The process includes five major steps: (i) hetero-Michael reaction between an alcohol and 1, (ii) stereoselective reduction of the resulting ketone, featuring stereochemical assistance of the neighboring oxazolidin-2-one group, (iii) esterification with an alkoxy acetic acid, (iv) chirality-transferring Ireland-Claisen rearrangement of the resulting 3-alkoxyallyl glycolate ester to provide a syn-2,3-dialkoxy carboxylate ester, and (v) relay ring-closing olefin metathesis to form a medium-ring ether along with the simultaneous removal of the oxazolidin-2-one moiety. 相似文献
993.
Justyna ?awecka 《Tetrahedron letters》2008,49(4):723-726
A new route to thiacrown ethers 5a-d and 6a-d incorporating a 2,2′-bipyridine subunit is elaborated using, (1) homo-coupling of 1,2,4-triazine sulfides 3a-d tethered to poly(ethylene glycol) chains with potassium cyanide and (2) Diels-Alder/retro Diels-Alder reaction with norbornadiene or 1-pyrrolidino-1-cyclopentene as the key steps. 相似文献
994.
Dutot L Gaucher A Elkassimi K Drapeau J Wakselman M Mazaleyrat JP Peggion C Formaggio F Toniolo C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(10):3154-3163
A new set of beta-amino acids that carry various crown ether receptors on their side chains of the general formula (S)-beta(3)-HDOPA(crown ether) (HDOPA: homo-3,4-dihydroxyphenylalanine; (crown ether): [15]crown-5 ([15-C-5]), [18]crown-6 ([18-C-6]), [21]crown-7 ([21-C-7]), 1,2-Benzo-[24]crown-8 ([Benzo-24-C-8]) and (R)-Binol-[20]crown-6 ([(R)-Binol-20-C-6])) was prepared. Peptides that are based on these new crowned beta-amino acids combined with (1S,2S)-ACHC (2-aminocyclohexanecarboxylic acid), which is known to be a potent 3(14)-helix inducer, to the hexamer level, with two crowned residues at the i and i+3 positions of the main-chain, were synthesized in solution by stepwise coupling using Boc-N(alpha)-protection (Boc: tert-butoxycarbonyl) and the EDC/HOAt C-activation method. Their conformational analysis was performed by using FTIR absorption, NMR and CD spectroscopy techniques. Our results are in full agreement with a 3(14)-helix conformation. 相似文献
995.
996.
A simple, green and efficient method for the DHP protection of various alcohols and phenols and the subsequent removal of the corresponding protective group in the presence of a catalytic amount of the activated carbon supported H2SO4 is described. 相似文献
997.
S. P. Gromov A. I. Vedernikov E. N. Ushakov M. V. Alfimov 《Russian Chemical Bulletin》2008,57(4):793-801
The results of the comprehensive study of novel supramolecular donor-acceptor complexes of bis(crown)stilbenes and bis(crown)azobenzene
with viologen analogs are generalized. The original methodology for self-assembling of the organic donor-acceptor complexes
possessing a very high thermodynamic stability is described. The hydrogen bonds between the peripheral fragments of the donor
and acceptor play the key role in the self-assembling. The influence of different structural factors on the thermodynamic
stability of the supramolecular donor-acceptor complexes and the efficiency of charge-transfer interactions between the donor
and acceptor are discussed. The driving forces of the reaction leading to exotic trimolecular charge-transfer complexes are
considered.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 779–787, April, 2008. 相似文献
998.
I. G. Ovchinnikov O. V. Fedorova P. A. Slepukhin G. L. Rusinov 《Russian Chemical Bulletin》2008,57(1):212-214
The photoinitiated [2+2]-cycloaddition of 1,5-bis[2-(3-phenyl-3-oxoprop-1-en-1-yl)phenoxy]-3-oxapentane in solution was studied.
In the presence of potassium cations, the reaction is intramolecular and gives crown ether containing the γ-truxin-type cyclobutane
fragment (anti, head-to-head) as the major product.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 204–206, January, 2008. 相似文献
999.
Małgorzata Jóźwiak 《Journal of Thermal Analysis and Calorimetry》2008,93(3):701-705
Enthalpies of solution of 1,4-dioxane, 12-crown-4 ether (12C4), 15-crown-5 ether (15C5) and 18-crown-6 (18C6) have been analyzed
from the point of view of preferential solvation of these cyclic ethers (crown ethers) by a molecule of acetone or dimethylsufoxide
in the mixtures of water with acetone or dimethylsulfoxide. It has been observed that the carbonyl carbon atom replacement
in acetone molecule by sulfur atom brings about completely different behavior of molecules of these solvents in relation to
cyclic ethers dissolved in mixed solvents. Crown ethers are preferentially solvated by acetone (ACN) molecules, which is not
observed in the case of dimethylsulfoxide (DMSO). 相似文献
1000.