Shao-Jie Lou

Mild and Versatile Nitrate-Promoted CH Bond Fluorination†

A novel and facile C-H bond fluorination proceeds under remarkably mild conditions (close to room temperature in most cases). Both aromatic and olefinic C(sp(2))-H bonds with a wide range of electronic properties are selectively fluorinated in the presence of a catalytic amount of simple, cheap, and nontoxic nitrate as the promoter. A Pd(II)/Pd(IV) catalytic cycle that is initiated by an in situ generated cationic [Pd(NO3)](+) species was proposed based on preliminary mechanistic studies.

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

Nitrate-promoted Selective C–H Fluorination of Benzamides and Benzeneacetamides

A versatile and site-selective nitrate-promoted C-H bond fluorination using various weak coordinating amides as intrinsic directing groups was developed. Diverse tertiary and secondary amides underwent selective aromatic C-H bond fluorination, which features broad substrate scope, good regioselectivity, and mild conditions. Moreover, the late-stage C-H bond fluorination of the challenging benzeneacetamides via distal directing was reported for the first time.

2-[3-(2-Acetoxyphenyl)quinoxa-lin-2-yl]phenyl acetate.

The title compound, C24H18N2O4, crystallizes as a syn-conformer, with dihedral angles between the quinoxaline moiety and the acetoxy-substituted benzene rings of 53.46 (3)° and 54.78 (3)°. In the crystal, the molecules form chains along [100] via C—H⋯O interactions.