Highly effective and stable catalysts based on d-metal oxides and fluorides were developed, and their selectivity in the synthesis of compacted heterocycles was proven. A unique method for synthesizing quinoline and methylquinolines in the vapor phase was proposed. It was shown that when equimolecular amounts of aniline and acetaldehyde are passed over the catalyst surface at a temperature range of 380-440°C, quinoline derivatives are formed with high yields. The temperature, height of the catalyst layer, and rate of delivery of raw material to the reactor were determined for the yield of quinoline. Additionally, the mechanism of 4-methylquinoline formation, contrary to Scroop's rule, was established.