Enantioselective Michael reaction of nitroalkanes onto nitroalkenes catalyzed by cinchona alkaloid derivatives
摘要:
An effective asymmetric synthesis of optically active 1,3-dinitro compounds via the direct Michael addition of nitroalkanes onto nitroalkenes has been described. In the presence of readily modified cinchona alkaloid derivatives, nitroethane reacted well with a variety of aromatic and heterocyclic aromatic nitroalkenes to afford products with good diastereoselectivities (dr up to 72/28) and enantioselectivities (ee up to 94%). The catalyst loading can be decreased to 2 mol % without compromising the asymmetric induction or the reaction rate. (C) 2012 Elsevier Ltd. All rights reserved.
In HF-SbF5, in the presence of H2O2 (Source of OH+ equivalent) quinine la yields 10-keto derivatives 4a and 5a and cyclic ether 3 as the major product. In the same conditions 1b, 2a, and 2b give the 10-keto and 10-fluoro-3-hydroxy analogs. (c) 2006 Elsevier Ltd. All rights reserved.