Ytterbium triflate-catalyzed conjugate addition of β-ketoesters to activated 1,4-naphthoquinones
摘要:
An efficient procedure for the conjugate addition of various beta-ketoesters to activated 1,4-naphthoquinones using a catalytic amount of Yb(OTf)(3) was developed. The tri-, tetra-, and pentacyclic adducts were obtained in very good to excellent yield. Cyclic beta-ketoesters added smoothly to activated quinones when compared to their acyclic counterparts. (C) 2008 Elsevier Ltd. All rights reserved.