Inter- and Intramolecular Imino Diels-Alder Reactions Catalyzed by Sulfamic Acid: A Mild and Efficient Catalyst for a One-Pot Synthesis of Tetrahydroquinolines

Abstract

The successful use of sulfamic acid as a catalyst in the inter- and intramolecular Inverse Electron Demand Diels-Alder reactions of iminodienes is described. A one-pot synthesis of tetrahydroquinolines was achieved by three component coupling of benzaldehyde and anilines with electron-rich dienophiles such as 2,3-dihydrofuran, dihydropyran and cyclopentadiene catalyzed by sulfamic acid (H2NSO3H). The intramolecular cycloaddition of imines, derived from O-prenylsalicylaldehyde with anilines catalyzed by sulfamic acid proceeds smoothly and yielded the diastereomeric tetrahydrochromanoquinolines in good yields.