Xingyi Zhu

Mechanically activated synthesis of 1,3,5-triaryl-2-pyrazolines by high speed ball milling

An efficient mechanically activated solvent-free synthesis of 1,3,5-triaryl-2-pyrazolines from chalcones and phenylhydrazines using high speed ball milling is described. This method has notable advantages in terms of good yield, short reaction time and neat conditions.

Mechanically Activated Solid-State Synthesis of Flavones by High-Speed Ball Milling

Abstract An efficient, mechanically activated solid-state synthesis of flavones from 1-(2-hydroxyphenyl)-3-aryl-1,3-propanediones using high-speed ball milling is described. This method has notable advantages in terms of good yield, short reaction time, and neat conditions.

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