Synthesis of chromeno[3,4-b]quinoline derivatives by heterogeneous [Cu(II)BHPPDAH] catalyst without being immobilized on any support under mild conditions using PEG 300 as green solvent

The efficient synthesis of chromeno[3,4-]quinoline derivatives by condensation of O-propargylated salicylaldehyde, or corresponding compounds and primary aromatic amine derivatives using a catalytic amount of heterogeneous Cu(II)BHPPDAH complex without being immobilized on any supports (5.0 mol%) in PEG 300 as a green solvent is described. The remarkable features of this protocol are good to high yields in all cases, short reaction times, a cleaner reaction profile in an environmentally benign solvent (PEG 300), and the method is applicable to large-scale operation without any problem. Furthermore, the catalyst was quantitatively recovered from the reaction mixture by simple filtration and reused at least seven times with almost consistent activity.