Wei-Ke Su

Europium Triflate–Catalyzed One‐Pot Synthesis of 2,4,5‐Trisubstituted‐1H‐imidazoles via a Three‐component Condensation

Abstract A simple, efficient, and practical procedure for synthesis of 2,4,5‐trisubstituted‐1H‐imidazoles via the condensation of benzoin or acetoin, aromatic aldehydes, and ammonium acetate using europium triflate [Eu(OTf)3] as a novel catalyst in high yields is described. The catalyst can be recovered conveniently and reused at least four times without any loss of activity.

Erlenmeyer Synthesis for Azlactones Catalyzed by Ytterbium(III) Triflate under Solvent‐Free Conditions

Abstract A series of 4‐arylidene‐2‐phenyl‐5(4)‐oxazolones were synthesized from cyclodehydration–condensation of hippuric acid, aromatic aldehydes, and acetic anhydride catalyzed by ytterbium(III) triflate under mild conditions in excellent yields.

Friedel–Crafts Acylation of Ferrocene Catalyzed by Immobilized Ytterbium(III) Triflate in Ionic Liquid

Abstract Ytterbium triflate [Yb(OTf)3]–catalyzed Friedel–Crafts acylation of ferrocene with anhydrides or acyl chlorides in n‐butylpyridinium tetrafluoroborate (BPyBF4) ionic liquid proceeded smoothly under mild conditions. The immobilized catalytic system (solvent/catalyst) was easily recovered and reused without any loss of activity. Chemoselective monoacylferrocenes were obtained in high yields by this catalytic system.

Copper Triflate–Catalyzed Cross‐Aldol Condensation: A Facile Synthesis of α,α′‐Bis(Substituted Benzylidene) Cycloalkanones

Abstract A facile, efficient, and clean procedure is described for synthesis of α,α′‐bis(substituted benzylidene) cycloalkanones with good yields by the reaction of cycloalkanones with aromatic aldehydes using Cu(OTf)2 as catalyst. The catalyst was easily recovered and reused without loss of activity.

Ytterbium Triflate Catalyzed Friedel–Crafts Reaction: Facile Synthesis of Diaryl Ketones

Abstract Friedel–Crafts reaction of aromatic compounds (benzenes, thiophene, furan, pyrrole, naphthalene, and benzothiophene) with bis(trichloromethyl) carbonate [BTC] was efficiently catalyzed by ytterbium triflate [Yb(OTf)3] to give diaryl ketones with moderate to good yields.

Novel Process for Synthesis of 1,2,4‐Triazoles: Ytterbium Triflate–Catalyzed Cyclization of Hydrazonyl Chlorides with Nitriles

Abstract A series of 1,3,5‐trisubstituted 1,2,4‐triazoles were synthesized via the intermolecular cyclization of hydrazonyl chlorides with nitriles catalyzed by ytterbium triflate [Yb(OTf)3]. The amount of catalysis was discussed and Yb(OTf)3 could be reused without loss of activity.

First Vilsmeier-Haack Synthesis of Flavones using bis-(Trichloromethyl) Carbonate/Dimethylformamide

Flavones are a class of naturally occurring compounds with various biological activities. 1–4 One of the most commonly used methods for the synthesis of flavones is the cyclodehydration of 1-(2-hydroxyphenyl)-3-aryl-1,3-propanediones. Many of these procedures use strong acids such as H2SO4, 5-6 HCl, 7 HBr or HI, 8 catalysts such as NaHSO4/SiO2, 9 H3PMo12O40·nH2O/SiO2, 10 H3PW12O40·nH2O/SiO2, 10 non-aqueous cation-exchange resin, 11 or supported trifluoromethanesulfonic acid. 12 All of these agents require high temperatures to complete the reaction. Other methods include the use of Br2 or I2 under irradiation conditions, 13 ionic liquid [EtNH3]NO3, 14 CuCl2, 15 or montmorillonite K-10 clay 16 as the catalyst by microwave-assisted synthesis have been reported in various yields. The Vilsmeier-Haack reaction was initially used for the formylation of activated aromatic substrates and carbonyl compounds. 17 It is now used as a powerful synthetic tool for the construction of many heterocyclic compounds such as quinolines, indoles, pyridines, and quinazoline derivatives. 18–23 However, its application to cyclodehydration reactions has not been reported. Following our recent work, 24–29 we carried out an investigation on the feasibility of cyclodehydration of 1-(2-hydroxyphenyl)-3-aryl-1,3-propanediones under Vilsmeier-Haack conditions with bis-(trichloromethyl) carbonate/dime-thylformamide (BTC/DMF) to synthesize flavones (Scheme 1). Firstly, the ratio of reactants was investigated. It was shown that using 1,2dichloroethane as the solvent, BTC/DMF/1-(2-hydroxyphenyl)-3-aryl-1,3-propanedione = 1:3:1.5 was optimum to obtain the desired product in good yields. If the ratio was decreased, the yield was reduced dramati-cally. Several conventional organic solvents such as DMF, diethyl ether, THF, toluene, and halohydro-carbons were used to optimize the reaction conditions. 1,2-dichloroethane and DMF were found to be more suitable solvents for the reaction under similar conditions because of their excellent solvating properties. When

5-Pyrrolidin-2-yltetrazole-Promoted One-Pot Hantzsch Polyhydroquinoline Synthesis Using NH4HCO3 as Nitrogen Source

A straightforward and green synthesis of polyhydroquinoline derivatives was reported via a four-component coupling reaction of aldehydes, dimedone, active methylene compounds, and ammonium bicarbonate in the presence of 5-pyrrolidin-2-yltetrazole under solvent-free conditions. The method offers several advantages including high yields, an environmental friendly procedure, a short reaction time, and easy isolation of products.

Ytterbium(III) Triflate–Catalyzed Stereoselective Synthesis of β‐Lactams via [2+2] Cyclocondensation in Ionic Liquid

Abstract Catalyzed by ytterbium(III) triflate [Yb(OTf)3], β‐lactams were stereoselectively synthesized from imines and acetyl chlorides in ionic liquid under mild conditions. The ionic liquid and catalyst could be recycled and reused as opposed to traditional solvent–catalyst systems.

One‐Step Reaction of Friedel–Crafts Acylation and Demethylation of Aryl‐Methyl Ethers Catalyzed by Ytterbium(III) Triflate

Abstract Catalytic amount of ytterbium(III) triflate [Yb(OTf)3] has been used to catalyze Friedel–Crafts acylation and demethylation of aryl‐methyl ethers in one‐step reaction to produce hydroxyacylphenones with moderate yields under mild conditions.