Microwave-assisted One-pot Synthesis of 7-Dimethylamino-4-Aryl-2- methylamino-3-nitro-4H-chromenes

Abstract

4-Aryl-2-amino-4H-chromenes possessing N,N-dimethylamino group have been reported as potential anticancer drugs. Despite few synthetic methods reported in the literature for their synthesis, there appear to be no reports on the direct use of N,N-dimethyl-3-aminophenol for the synthesis of 4- aryl-2-methylamino-3-nitro-4H-chromenes. One-pot condensation of N,N-dimethyl-3-aminophenol, aromatic aldehydes and (E)-N-methyl-1-(methylthio)-2-nitro-ethenamine was carried out using MW irradiation to get the 4-aryl-2-methylamino-3-nitro-4H-chromenes under catalyst-free conditions. This transformation presumably occurs via o-quinone methide formation, Michael addition-intramolecular O-cyclization-elimination sequence of reactions creating new two C-C bonds and one C-O bond. Various substituted aromatic aldehydes reacted smoothly with N,N-dimethyl-3-aminophenol and (E)-Nmethyl- 1-(methylthio)-2-nitro-ethenamine to give the corresponding 4-aryl-2-methylamino-3-nitro-4Hchromenes in good yields. We have developed a one-pot three component condensation of N,Ndimethyl- 3-aminophenol, aromatic aldehyde and NMSM for the synthesis of N,N-dimethylamino substituted 4-aryl-2-methylamino-3-nitro-4H-chromenes in good yields. The significant features of this reaction include catalyst-free, solvent free, no column chromatographic purification, short reaction time and good yields.