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Triphenylbismuth diacylates, Ph3Bi(O2CR)2 (R = Me, Et, Ph, CF3, CH=CH2), are novel effective reagents for fine organic synthesis. They oxidize primary and secondary alcohols and di-tert-glycols under mild conditions to form the corresponding carbonyl compounds in high yields;O- andN-phenylate alcohols, enols, and amines; andO- ando-C-phenylate phenols.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2043–2047, December, 1993. 相似文献
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The family of allylation reactions developed by Tsuji in the 1980s are capable of generating tertiary and quaternary carbon stereocenters from several synthetic precursors. Despite the utility of these transformations, they have seen little use in the synthesis of natural products. Recently, the power of these reactions was significantly enhanced by the development of enantioselective versions of these transformations. Applications of these methods to the enantioselective syntheses of natural products and pharmaceutical compounds highlight the importance of these developments. 相似文献
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Various ligands, such as (Z)‐1‐phenyl‐2‐[(4S)‐4‐phenyl‐4,5‐dihydro‐1,3‐oxazol‐2‐yl]ethen‐1‐ol ((S)‐ 1a ) and (Z)‐1‐phenyl‐2‐[(4S)‐4‐phenyl‐4,5‐dihydro‐1,3‐thiazol‐2‐yl]ethen‐1‐ol ((S)‐ 1c ), were investigated as auxiliaries for the asymmetric synthesis of chiral ruthenium(II) complexes. The reaction of these chiral auxiliary ligands with [RuCl2(dmso)4], 2,2′‐bipyridine (bpy, 2.2 equiv), and triethylamine (10 equiv) in DMF/PhCl (1:8) at 140 °C for several hours diastereoselectively provided the complexes Λ‐[Ru(bpy)2{(S)‐ 1a ? H}] (Λ‐(S)‐ 2a , 52 % yield, 56:1 d.r.) and Λ‐[Ru(bpy)2{(S)‐ 1c ? H}] (Λ‐(S)‐ 2c , 48 % yield, >100:1 d.r.) in a single step after purification. Both Λ‐(S)‐ 2a and Λ‐(S)‐ 2c could be converted into Λ‐[Ru(bpy)3](PF6)2 by replacing the bidentate enolato ligands with bpy, under retention of configuration, induced by either NH4PF6 as a weak acid (from Λ‐(S)‐ 2a : 73 % yield, 22:1 e.r.; from Λ‐(S)‐ 2c : 77 % yield, 22:1 e.r.), TFA as a strong acid (from Λ‐(S)‐ 2a : 72 % yield, 52:1 e.r.; from Λ‐(S)‐ 2c : 85 % yield, 25:1 e.r.), methylation with Meerwein′s salt (from Λ‐(S)‐ 2a : 59 % yield, 46:1 e.r.; from Λ‐(S)‐ 2c : 86 % yield, 37:1 e.r.), ozonolysis (from Λ‐(S)‐ 2a : 56 % yield, 22:1 e.r.; from Λ‐(S)‐ 2c : 43 % yield, 6.3:1 e.r.), or oxidation with a peroxy acid (from Λ‐(S)‐ 2a : 72 % yield, 45:1 e.r.; from Λ‐(S)‐ 2c : 79 % yield, 8.5:1 e.r.). This study shows that, except for the reaction with NH4PF6, oxazoline‐enolato complex Λ‐(S)‐ 2a provides Λ‐[Ru(bpy)3](PF6)2 with higher enantioselectivities than analogous thiazoline‐enolato complex Λ‐(S)‐ 2c , which might be due to the higher coordinative stability of the thiazoline‐enolato complex, thus requiring more prolonged reaction times. Thus, this study provides attractive new avenues for the asymmetric synthesis of non‐racemic ruthenium(II)‐polypyridyl complexes without the need for using a strong acid or a strong methylating reagent, as has been the case in all previously reported auxiliary methods from our group. 相似文献
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M. Agostinha R. Matos Margarida S. Miranda Victor M. F. Morais Joel F. Liebman 《Molecular physics》2013,111(12):1833-1841
The standard molar enthalpy of formation in the gas phase of 2H-1,4-benzoxazin-3(4H)-one was derived from the standard energy of combustion determined by static bomb combustion calorimetry in oxygen atmosphere and from the standard sublimation enthalpy determined by Calvet microcalorimetry. In addition, we report the results of a systematic theoretical study of the keto and enol tautomers in benzoxazinones and diones using density functional theory. The keto tautomers are computed to be more stable than the enols. Tautomerization energies are reported. 相似文献
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16O/18O Exchange of Aldehydes and Ketones caused by H218O in the Mechanistic Investigation of Organocatalyzed Michael,Mannich, and Aldol Reactions
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Prof. Dr. Yujiro Hayashi Dr. Takasuke Mukaiyama Dr. Meryem Benohoud Dr. Nishant R. Gupta Tsuyoshi Ono Shunsuke Toda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5868-5872
Organocatalyzed Michael, Mannich, and aldol reactions of aldehydes or ketones, as nucleophiles, have triggered several discussions regarding their reaction mechanism. H218O has been utilized to determine if the reaction proceeds through an enamine or enol mechanism by monitoring the ratio of 18O incorporated into the final product. In this communication, we describe the risk of H218O as an evaluation tool for this mechanistic investigation. We have demonstrated that exchange of 16O/18O occurs in the aldehyde or ketone starting material, caused by the presence of H218O and amine catalysts, before the Michael, Mannich, and aldol reactions proceed. Because the newly generated 18O starting aldehydes or ketones and 16O water affect the incorporation ratio of 18O in the final product, the use of H218O would not be appropriate to distinguish the mechanism of these organocatalyzed reactions. 相似文献
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Treatment of α,β‐unsaturated ketones with an electrophilic site at the γ‐position in the presence of trimethylsilyl cyanide with bis(iodozincio)methane afforded the (Z)‐silyl enol ether of the β‐cyclopropyl substituted ketone in good yields. The reaction proceeds by 1,4‐addition to form an enolate, and its sequential intramolecular nucleophilic attack to an adjacent electrophilic site. The reaction of γ‐ethoxycarbonyl‐α,β‐unsaturated ketone and bis(iodozincio)methane in the presence of trimethylsilyl cyanide afforded 1‐ethoxy‐1‐trimethylsiloxycyclopropane derivatives, which can be regarded as the homoenolate equivalent. Additionally, reaction of the obtained homoenolate equivalents with imines give 1‐(E)‐alkenyl‐2‐(1‐aminoalkyl)alkanols diastereoselectively. 相似文献