Yunkui Liu

Facile and efficient one-pot synthesis of 2-arylbenzoxazoles using hydrogen tetrachloroaurate as catalyst under oxygen atmosphere

In this paper, we presented a novel method for the facile and efficient one-pot synthesis of 2-arylbenzoxazoles, which were directly synthesized from 2-aminophenol and aldehydes catalyzed by hydrogen tetrachloroaurate (HAuCl4·4H2O) under an oxygen atmosphere with anhydrous tetrahydrofuran (THF) as solvent or in solvent-free condition. The results show that this method could bring excellent yields as high as 96%. THF was proven to be the best choice among several solvents screened and the reaction was tolerated with a variety of aromatic aldehydes possessing electron-donating or withdrawing groups. The advantages of the present method lie in catalytic process using economic and environmentally benign dioxygen as oxidant.

Oxidative Aromatization of 1,3,5-Trisubstituted Pyrazolines Using Hydrogen Tetrachloroaurate as Catalyst Under an Oxygen Atmosphere

Today gold is without a doubt the “star metal” in chemistry because of the focus of attention on gold-catalyzed organic transformations in recent years.1–7 Among various new transformations catalyzed by gold, those involving nucleophilic additions to C-C multiple bonds (alkynes, alkenes or allenes)8–10 and catalytic C-H bond functionalization11,12, have been studied intensively. In contrast, gold-catalyzed oxidation chemistry, in particular gold as heterogeneous and/or homogeneous catalyst for selective oxidation reactions with economic and environmentally benign oxidants, such as dioxygen or hydrogen peroxide, has been less developed.13 Thus far, representative oxidation transformations are mainly limited in oxidation of monoxide,14–16 alcohols,17–24 amines25,26 and sulfides,27,28 epoxidations of olefins,29 oxidative cleavage of carbon-carbon multiple bonds,30,31 etc. Therefore, it is still desirable to extend gold-catalyzed oxidation chemistry. 1,3,5-trisubstituted pyrazoles are one class of important compounds because heterocycles containing pyrazole moieties often exhibit valuable biological and medicinal activities, such as analgestic, anti-inflammatory, antipyretic, anti-arrhythmic, psychoanaleptic, antidiabetic and antibacterial ones.32–37 Generally, oxidative aromatization of 1,3,5-trisubstituted pyrazolines which could be easily prepared from the condensation of chalcones with arylhydrazines,38 is the most widely used protocol for synthesis of 1,3,5-trisubstituted pyrazole derivatives. To date, a variety of oxidants have been used for the purpose, e.g. zirconium (IV) nitrate,39 lead (IV) tetraacetate,40 silver (I) nitrate,41 bismuth (III) nitrate,42 manganese (IV) dioxide,43 potassium permanganate,44 mercury (II) oxide,45 iodobenzene diacetate,46 sodium nitrite and sodium nitrate in acetic acid,47 trichloroisocyanuric acid,48 4-(p-chloro)phenyl-1,3,4-triazole-3,5-dione,49 Pd/C,50 iodine pentoxide or iodic acid,51 activated carbon/oxygen system,52 and N-hydroxyphthalimide (NHPI)/cobalt acetate/oxygen sytem,53 etc. However, these processes have one or more limitations including high catalyst

Copper(0)/Selectfluor System-Promoted Oxidative Carbon–Carbon Bond Cleavage/Annulation of o-Aryl Chalcones: An Unexpected Synthesis of 9,10-Phenanthraquinone Derivatives

A general and efficient protocol for the synthesis of 9,10-phenanthraquinone derivatives has been successfully developed involving a copper(0)/Selectfluor system-promoted oxidative carbon-carbon bond cleavage/annulation of o-aryl chalcones. A variety of substituted 9,10-phenanthraquinones were synthesized in moderate to good yields under mild reaction conditions.

Sodium tetrachloroaurate(III) dihydrate-catalyzed efficient synthesis of 1,5-benzodiazepine and quinoxaline derivatives.

Both 1,5-benzodiazepine and quinoxaline derivatives are important heterocycles in pharmaceuticals. We describe an efficient and clean method for the synthesis of 1,5-benzodiazepines from o-phenylenediamine and ketones catalyzed by sodium tetrachloroaurate(III) dihydrate under mild conditions. The catalyst was shown to be equally effective for the synthesis of quinoxalines from o-phenylenediamine and α-bromo ketones under the similar reaction conditions. This method produced good yields.

Sm/HOAc/EtOH System-Mediated Reduction of Baylis-Hillman Acetates

Abstract Selective formation of (2E)‐2‐methylalk‐2‐enoates or 2‐methyl alkanoates could be achieved in moderate to good yields under mild conditions via Sm/HOAc/EtOH system–mediated reduction of Baylis–Hillman acetates depending on the amount of samarium consumed in the reactions.

3,5-Dichloro-6-morpholinopyridin-2-yl diethyl thiophosphate

In the title compound, C13H19Cl2N2O4PS, the morpholine ring adopts a chair conformation. The P=S bond distance is 1.9050 (8) A.