One-pot organocatalytic enantioselective Michael addition and aza-cyclization/dehydration cascade reaction strategy: asymmetric synthesis of highly functionalized 1,4-dihydroquinolines

A methodology for the synthesis of enantioenriched, highly functionalized 1,4-dihydroquinolines has been developed on the basis of the enantioselective Michael addition of beta-keto esters with N-protected-2-amino-beta-nitrostyrenes using an organocatalyst followed by in situ aza-cyclization/dehydration cascade reaction. Asymmetric catalytic reactions using quinine-derived squaramide as an organocatalyst afforded the desired 1,4-dihydroquinolines in good yields and with excellent enantioselectivities (up to 95.8:4.2 er). (C) 2015 Published by Elsevier Ltd.