Heng Jiang

Inorganic Zinc Salts Catalyzed Knoevenagel Condensation at Room Temperature without Solvent

Abstract The Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile or ethyl cyanoacetate), catalyzed by inexpensive and readily available Zn(OAc)2·2H2O, ZnCl2, and ZnBr2 to prepare arylidene compounds in excellent yields under solvent-free conditions at room temperature has been described.

Acetic Acid-Assisted Copper Methanesulfonate Catalyst for Chemoselective Conversion of Aldehydes to Acylals

Abstract A new catalytic system has been discovered by combining copper methanesulfonate with acetic acid for chemoselective conversion of aldehydes to acylals in high yields at ambient temperature under solvent‐free conditions. The efficiency of this system might result from the “double activation” of Brønsted–Lewis acid catalysis on aldehydes.

Praseodymium Methanesulfonate Catalyzed One‐Pot Synthesis of 3,4‐Dihydropyrimidin‐2‐(1H)‐ones

Abstract A series of 3,4‐dihydropyrimidin‐2‐(1H)‐ones compounds was synthesized efficiently by a one‐pot cyclocondensation of an aldehyde, 1,3‐dicarbonyl compound, and urea in absolute ethanol under refluxing temperature using praseodymium methanesulfonate as catalyst. After the reaction, the catalyst can be easily recovered and reused several times without distinct decrease in reaction yields.

Synthesis of 1,1‐Diacetates using a New Combined Catalytic System: Copper p‐Toluenesulfonate/HOAc

Abstract Copper p‐toluenesulfonate acetic acid has been established as an efficient combined catalytic system for chemoselective conversion of aldehydes to diacetates in high yields at ambient temperature in short reaction times. For the catalytic system, the amount of copper p‐toluenesulfonate reduced to 0.3 mol%. After the reaction, copper p‐toluenesulfonate can be easily recovered and reused for at least 10 runs.

Three-Component Mannich Reaction of Aromatic Ketones, Aldehydes and Amines Catalyzed by Reusable Aluminium Methanesulfonate

Mannich type reactions are very important carbon-carbon bond forming reactions in organic synthesis and one of the most useful methods for the preparation of β-aminocarbonyl compounds, which are valuable synthetic intermediates for pharmaceuticals and natural products.1 Among the three-component reactions, the Mannich processes have elicited enormous interest and several procedures for the synthesis of β-aminocarbonyl compounds have been widely described in the literature.2 Earlier literature reported that β-aminocarbonyl compounds derived from aromatic ketones, aldehydes and amines can only be realized indirectly by “amine exchange reaction” or “the addition of ketones to Schiff bases”.3,4 Yi and co-workers described the three-component Mannich reaction of aromatic ketones, aldehydes and amines could be catalyzed by HCl/EtOH in 1991.5 Since then, the Mannich reaction has been expanded to include various ketones, aldehydes and amines using HCl/EtOH.6 However, the hydrochloride salts of the Mannich bases using HCl/EtOH are unstable on standing.5 Furthermore, hydrochloric acid is environmentally unfriendly. Therefore, more practical synthetic methods for these multiply-substituted Mannich bases have been reported, using dodecylbenzenesulfonic acid,7 polystyrene-SO3H, NbCl5, Re(PFO)3, Re(OPf)3, an acidic ionic liquid,12 H3PW12O40, NaBAr4, SiO2-OAlCl2, QAS gemini fluorosurfactant,16 etc. However, several drawbacks such as large excesses of catalyst, expensive reagents, long reaction time, and low yields still exist. Moreover, the Mannich reaction of ortho-substituted aromatic amine gave none of desired product due to steric effects. In addition, conventional Lewis acid cannot be used because of the presence of free amines and water produced in the imine formation. Thus, from atom-economy and environmental standpoints, it is desirable to develop a new efficient system for the direct one-pot Mannich reaction.

WATER-TOLERANT AND REUSABLE LEWIS ACID CATALYST FOR THE ONE-POT SYNTHESIS OF 3,4-DIHYDROPYRIMIDIN-2-(1H)-ONES UNDER SOLVENT-FREE CONDITIONS

3,4-Dihydropyrimidin-2-(1H)-ones were synthesized in high yields by a one-pot cyclocondensation of an aldehyde, a 1,3-dicarbonyl compound, and urea using copper methanesulfonate (2 mol%) as a recyclable catalyst under solvent-free conditions in short reaction time (1–2 h).

RESEARCH OF THERMAL DECOMPOSITION OF HYDRATED METHANESULFONATES

Hydrated methanesulfonates Ln(CH3SO3)3·nH2O (Ln=La, Ce, Pr, Nd and Yb) and Zn(CH3SO3)2·nH2O were synthesized. The effect of atmosphere on thermal decomposition products of these methanesulfonates was investigated. Thermal decomposition products in air atmosphere of these compounds were characterized by infrared spectrometry, the content of metallic ion in thermal decomposition products were determined by complexometric titration. The results show that the thermal decomposition atmosphere has evident effect on decomposition products of hydrated La(III), Pr(III) and Nd(III) methanesulfonates, and no effect on that of hydrated Ce(III), Yb(III) and Zn(II) methanesulfonates.

Copper nitrate catalyzed three-component one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones.

Abstract An efficient synthesis of 3,4-dihydropyrimidin-2(1H)-ones from aldehydes, 1,3-dicarbonyl compounds, and urea using copper nitrate under refluxing temperature in ethanol was described. Compared with other Lewis copper salts, copper nitrate proved to be the most efficient. The advantages of the new method were good yields (61–93%), short reaction time (0.4–3 h), and inexpensive catalyst.