New Findings on the Cerium(IV) Ammonium Nitrate Catalyzed Povarov Reaction: Stereoselective Synthesis of 4-Alkoxy-2-aryl-1,2,3,4-tetrahydro-quinoline Derivatives

摘要: Cerium(IV) ammonium nitrate catalyzes the three-com- ponent, imino Diels-Alder (Povarov) reaction between anilines, ar- omatic aldehydes, and acyclic vinyl ethers, giving cis-4-alkoxy-2- aryl-1,2,3,4-tetrahydroquinolines with almost complete diastereo- selectivity. The corresponding starting from cyclic ethers gave two possible diastereomers, endo-com- pound as major product. This stereochemical outcome is ex- plained through a stepwise mechanism for reaction, this was subsequently proved by trapping putative oxonium intermediate in presence of ethanol.