New One‐Step Procedure for the Synthesis of 6H‐Chromeno[4,3‐b]quinolines and 8a,9,14,14a‐Tetrahydro‐8H‐benzo[5,6]chromeno[4,3‐b]quinolines.

Abstract

New One-Step Procedure for the Synthesis of 6H-Chromeno[4,3-b]quinolines and 8a,9,14,14a-Tetrahydro-8H-benzo[5,6]chromeno[4,3-b]quinolines. -Intramolecular cyclization of intermediate Schiff bases, generated in situ from allyloxybenzaldehyde (I) and anilines (II), occurs at a low rate under fairly severe conditions. The reaction does not produce the expected tetrahydrochromenoquinolines but their dehydrogenated analogues (III). Unlike aldehyde (I), the cyclization of napthalenecarbaldehyde derivative (IV) is not accompanied by dehydrogenation. Moreover, benzochromenoquinolines (VI) are formed as single diastereoisomers. -(TOMASHEVSKAYA, M. M.; TOMASHENKO, O. A.; TOMASHEVSKII, A. A.; SOKOLOV, V. V.; POTEKHIN, A. A.; Russ. J. Org. Chem. 43 (2007) 1, 77-82; St. Petersburg State Univ., St. Petersburg 198504, Russia; Eng.) -H. Hoennerscheid 28-140