1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) with ionic modification supported on magnetic nanoparticles was prepared and characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TG), vibrating sample magnetometer (VSM) and elemental analysis. The supported ionic specie was certified as a highly active and magnetically recoverable catalyst for the synthesis of various substituted ureas and structurally diverse N-heterocyclic compounds. The catalyst can be readily recovered by external magnetie and be reused for 6 times without significant loss in catalytic activity. Ionic tagged catalyst performs much better than its ionic-free counterpart in organic transformations.Keywords: Immobilization; Ionic moiety; Magnetic nanoparticles; Recyclability; TBD;

Propylamine modified with imidazolium ionic moiety grafted onto magnetic nanoparticles (MNPs) was prepared and evaluated as a catalyst for Knoevenagel condensation in water at room temperature. The catalyst was efficient in the reaction to give the condensation products in good yields. It is worth noting that the ionic-tagged catalyst performed significantly better than its ionic tag-free counterpart. Finally, the catalyst could be reused for 8 times with a slight loss in its catalytic activity.

A series of novel multiple-acidic ionic liquids, sulfated from the low-cost starting material 2-aminoethanol, were introduced as catalysts for the Henry reaction of versatile aldehydes and nitroalkane under solvent-free conditions. The ionic liquid with hydrogen sulfate as a counteranion showed the best catalytic efficiency and gave the corresponding trans-β-nitrostyrenes in good to excellent yields. More importantly, the ionic liquid catalyst could be readily recovered and reused six times without considerable loss of its catalytic activity.

An array of novel 1,4-diazobicyclo[2.2.2]octane (DABCO) based ionic liquids were developed and used as recyclable catalysts for the aza-Michael addition at room temperature without any organic solvent. [DABCO–PDO][OAc] was found to be the most efficient catalyst, and the amount of catalyst was only 10 mol %. Various amines reacted with a wide range of α,β-unsaturated amides, smoothly affording target products in good to excellent yields within hours. Moreover, the catalyst could be reused up to eight times, still maintaining a high catalytic activity. Finally, a plausible mechanism was proposed. FTIR and computational chemistry were used to verify the catalytic mechanism.

Glycerol was used as a reaction medium as well as promoter for aza-Michael addition of aromatic amines to electronic deficient α,β-unsaturated ketones. Various aromatic amines can react smoothly with chalcone, 2-cyclohexen-1-one, 2-cyclopenten-1-one, and ethyl vinyl ketone to achieve good to excellent yields in the absence of any catalyst.

An efficient and facile protocol for aza-Michael addition of aliphatic and aromatic amines to electron-deficit alkenes using [TMG][Lac] as catalyst under solvent-free conditions was established.

Knoevenagel condensation of aromatic aldehydes with active methylene compounds such as malononitrile, ethylcyanoacetate, and cyanoacetamide proceeded very smoothly in reusable and cheap ionic liquid 2-hydroxyethylammonium formate at room temperature in the absence of a catalyst. Compared to other reported ionic liquids, the ionic liquid 2-hydroxyethylammonium formate shows better potential in the applications on the industrial scale with its low cost and viscosity.

A simple and efficient method is proposed for the synthesis of tetrahydrobenzo[b]pyrans with aromatic aldehydes, active methylene compounds, and dimedone using basic ionic liquid catalyst in water. The procedure offers several advantages including short reaction time, good yield, easy procedure, and good recyclability of catalysts, which may be a practical alternative to conventional processes for preparation of 4-hpyrans.Download full-size image