efficient access to novel tetra- and pentacyclic dihydroquinolin-2-ones by catalyst-free domino knöevenagel hetero-diels–alder reactions from n-(2-formylphenyl)-n-methylcinnamamides and cyclic 1,3-dicarbonyls in water

An efficient catalyst-free synthesis of novel annulated hybrid derivatives of two known scaffolds, dihydroquinolinone and pyranopyranone, pyranopyrimidinedione, pyranocoumarin or chromenone is described. n-(2-formylphenyl)-n-methylcinnamamides underwent a one-pot domino knöevenagel hetero-diels–alder reaction with dimedone, n,n-dimethylbarbituric acid, 1,3-indanedione, 4-hydroxycoumarins and 4-hydroxy-6-methyl-2h-pyran-2-one in water, affording the desired tetra and pentacyclic pyranoquinolinones in excellent yields.