An appropriate One-Pot Synthesis of a Series of 7,7-Dimethyl-10-aryl-7,8-dihydro-5H-indeno[1,2-b]quinoline-9,11(6H,10H)-diones Using Tribromomelamine as an Efficient Organocatalyst

A mild and efficient protocol for the synthesis of 7,7-dimethyl-10-aryl-7,8-dihydro-5H-indeno[1,2-b]quinoline-9,11(6H,10H)-diones via a one-pot four component condensation of aromatic aldehydes, 1,3-indandione, dimedone and ammonium acetate using tribromomelamine (TBM) as a catalyst is described. The reaction occurs in ethanol to give the corresponding products in good to high yields in short times. The effect of various solvent and catalyst amount was investigated. The results of the presented protocol in comparison with the different available catalysts show that TBM presented better results. A possible mechanism for the formation of indeno[1,2-b]quinolines using TBM as a catalyst has been proposed. The salient features of the present method are: high yields, mild reaction conditions, simple and straightforward work-up, cost-effective and environmentally benign procedure.