Novel and Efficient Lewis Acids as Catalysts for Single-step Synthesis of Pyrano- and Furoquinolines

Some Lewis acids such as ZrCl4, SnCl4, TiCl4, and PtCl4 have been found to be novel and highly efficient catalysts for one-pot coupling of the three components, anilines, aldehydes, and 3,4-dihydro-2H-pyran or 2,3-dihydrofuran to produce the corresponding pyrano- or furoqinolines in high yields and high diastereoselectivity.