Highly Enantioselective Synthesis of Spiro[cyclohexanone-oxindoles] and Spiro[cyclohexanone-pyrazolones] by Asymmetric Cascade [5+1] Double Michael Reactions

The asymmetric catalytic synthesis of naturally occurring and biologically active spiro compounds is a challenge for modern chemical methodology. Here we report the construction of spiro compounds through cascade [5+1] double Michael reactions between divinyl ketones and N-unprotectedoxindoles or N-phenyl-protected pyrazolones catalyzed by a combination of the easily available 9-amino-9-deoxy-epi-quinine with N-Boc-D-phenylglycine. The desired multistereogenic spiro[cyclohexanone-oxindoles and -pyrazolones] were obtained with high yields (up to 98?%) andstereoselectivities (up to >20:1 dr, 99?% ee).