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). An efficient approach to spiro compounds through cascade [5+1] double Michael reactions between divinyl ketones and oxindoles or N‐protected pyrazolones in the presence of 9‐amino‐9‐deoxy‐epi‐quinine and N‐Boc‐D‐phenylglycine is reported. Multistereogenic spiro[cyclohexanone‐oxindoles and ‐pyrazolones] are obtained with high yields (up to 98 %) and stereoselectivities (up to >20:1 dr, 99 % ee).