Asymmetric tandem Michael addition/oxidation of pyrazolones with p-benzoquinone catalyzed by cinchona alkaloids

By employing a natural cinchona alkaloid as a catalyst, the enantioselective tandem Michael addition/oxidation of 4-substituted pyrazol-5-ones with p-benzoquinones was realized. The reaction afforded a wide range of 4,4-disubstituted pyrazol-5-ones with moderate to good yields (up to 72%) and moderate to good enantioselectivities (up to 99%). (C) 2015 Elsevier Ltd. All rights reserved.