Multicomponent reactions in unconventional solvents: state of the art

Potassium phthalimide-N-oxyl: a novel, efficient, and simple organocatalyst for the one-pot three-component synthesis of various 2-amino-4H-chromene derivatives in water

The synthesized nanocatalyst in this work provides a green and useful method to obtain 4 H -benzo[ b ]pyrans and dihydropyrano[ c ]chromenes in aqueous media. The catalyst shows environmental benign character, which can be easily prepared, stored, recovered without obvious significant loss of activity. Due to water-resistant and superparamagnetic nano-nature of the catalyst, it could be easily separated by the application of an external magnetic device and reused conveniently. The synthesized inorganic–organic hybrid nanocatalyst has fully been characterized by magnetic, adsorptive and thermal techniques (transmission and scanning electron microscopy (TEM & SEM), Fourier transform spectroscopy infrared (FTIR), thermo gravimetric analysis (TGA), X-ray Diffraction (XRD), Brunauer Emmett Teller (BET) and vibrational sampling magnetometer (VSM)), which reveal of the superparamagnetic nano-nature of the particles. In summary, the magnetically inorganic–organic hybrid nanocatalyst supported on hydroxyapatite encapsulated γ -Fe 2 O 3 was found to be quite excellent and clean catalytic system for the synthesis of 4 H -benzopyrans and 2-amino-5-oxo-4-aryl-4,5-dihydropyrano[3,2- c ]chromene-3-carbonitriles.

One-pot synthesis of 4H-benzo[b]pyrans and dihydropyrano[c]chromenes using inorganic–organic hybrid magnetic nanocatalyst in water

Nanozeolite clinoptilolite as a highly efficient heterogeneous catalyst for the synthesis of various 2-amino-4H-chromene derivatives in aqueous media

Update 1 of: Ionic liquids in heterocyclic synthesis.

Synthesis of 4H‐benzopyrans catalyzed by acyclic acidic ionic liquids in aqueous media

Some halogen-free acyclic task-specific ionic liquids (TSILs) were synthesized as novel and recyclable catalysts for the synthesis of 5-oxo-5,6,7,8-tetrahydro-4H-benzo[b]pyrans by one-pot three-component condensation of aromatic aldehyde, malononitrile (or ethyl cyanoacetate), and dimedone (or 1,3-cyclohexanedione) in water. The condensation accomplished successfully with good yields ranged from 86 to 94%. After the reaction, the products could simply be separated from the catalyst/water, and the catalyst could be reused at least 10 times without noticeably decreasing the catalytic activity. J. Heterocyclic Chem., 2010.

Hua-Bin Zhang

Papers

Synthesis of 4H‐benzopyrans catalyzed by acyclic acidic ionic liquids in aqueous media

Synthesis of 4H‐Benzopyrans Catalyzed by Acyclic Acidic Ionic Liquids in Aqueous Media.