An efficient synthesis of novel functionalized benzo[h]pyrano[2,3-b]quinolines and pyrano[2,3-b]quinoline derivatives via one-pot multicomponent reactions

In this paper, a convenient, one-pot, for the straightforward synthesis of pyrano[2,3-b]quinoline and benzo[h]pyrano[2,3-b]quinoline derivatives is presented, which includes a three-component reaction of (2-chloroquinoline-3-carbaldehyde, 2-chlorobenzo[h]quinoline-3-carbaldehyde), and 1-phenyl-2-(1,1,1-triphenyl-λ5- phosphanylidene)ethan-1-one (Wittig reagent) with the active methylene compounds such as (benzoylacetonitrile, dimedone, 1,3-dimethylbarbituric acid, 4-hydroxycoumarin and 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one), during the two processes of C–C bond formation (Michael addition) and intramolecular cyclization (by the attack of the oxygen atom of active methylene compounds). Advantages of this protocol include easily accessible starting materials, excellent yields (65–98%), absence of a metal catalyst and simple workup procedure (the pure products were obtained simply by washing the products with EtOH). A series of pyrano[2,3-b]quinoline and benzo[h]pyrano[2,3-b]quinoline derivatives have been synthesized in excellent yields (65–98%) via a one-pot three-component reaction of (2-chloroquinoline-3-carbaldehyde, 2-chlorobenzo[h]quinoline-3-carbaldehyde) and 1-phenyl-2-(1,1,1-triphenyl-λ5-phosphanylidene)ethan-1-one (Wittig reagent) with the active methylene compounds such as (benzoylacetonitrile, dimedone, 1,3-dimethylbarbituric acid, 4-hydroxycoumarin and 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one), during the two processes of C–C bond formation (Michael addition) and intramolecular cyclization (by the attack of the oxygen atom of active methylene compounds). Advantages of this protocol include easily accessible starting materials, excellent yields (65–98%), absence of a metal catalyst and simple workup procedure (the pure products were obtained simply by washing the products with EtOH).