Rapid preparation of pyranoquinolines using microwave dielectric heating in combination with fractional product distillation

4-Hydroxy-6-methyl-2H-pyrano[3,2-c]quinoline-2,5(6H)-dione was prepared by microwave-assisted cyclocondensation of N-methylaniline with 2 equiv of diethyl malonate. Key to the success of the synthesis was the use of open vessel controlled microwave heating technology, allowing the simultaneous removal of the formed ethanol from the reaction mixture by fractional distillation.