Asymmetric [3+3] Cycloaddition of <i>N</i> ‐Vinyl Oxindole Nitrones with 2‐Indolylmethanols to Prepare Spirooxindole[1,2]oxazines
Ning Zou, Yuzheng Wu, Xin‐Yi Zhong, Wei Cui, Wei Cui, Li‐Min Liao, Dong‐Liang Mo, Wen‐Jun Zhou, Wen‐Jun Zhou
Abstract
Abstract We describe a chiral phosphoric acid (CPA) catalyzed asymmetric [3+3] cycloaddition of N ‐viny oxindole nitrones with 2‐indolylmethanols to prepare various spirooxindole[1,2]oxazines in 43–93% yields and 88:12–97:3 enantiomeric ratios. Experimental results revealed that the addition of hexafluoroisopropanol (HFIP) played important roles to help CPA control the reaction reactivity and enantioselectivity. The present method features the construction of a tetrasubstituted chiral carbon stereocenter and the example of N ‐vinyl nitrones in asymmetric [3+3] cycloaddition.
Topics & Concepts
StereocenterCycloadditionChemistryOxindoleEnantioselective synthesisOxazinesEnantiomerOrganic chemistryOrganocatalysisMedicinal chemistryCombinatorial chemistryCatalysisOxidative Organic Chemistry ReactionsSynthesis of Indole DerivativesAsymmetric Synthesis and Catalysis