Blake E Daniels1, Jane Ni1, Sarah E Reisman2. 1. The Warren and Katharine Schlinger Laboratory of Chemistry and Chemical Engineering, Division of Chemistry and ChemicalEngineering, California Institute of Technology, Pasadena, CA 91125, USA. 2. The Warren and Katharine Schlinger Laboratory of Chemistry and Chemical Engineering, Division of Chemistry and ChemicalEngineering, California Institute of Technology, Pasadena, CA 91125, USA. reisman@caltech.edu.
Abstract
A conjugate addition/asymmetric protonation/aza-Prins cascade reaction has been developed for the enantioselective synthesis of fused polycyclic indolines. A catalyst system generated from ZrCl4 and 3,3'-dibromo-BINOL enables the synthesis of a range of polycyclic indolines in good yields and with high enantioselectivity. A key finding is the use of TMSCl and 2,6-dibromophenol as a stoichiometric source of HCl to facilitate catalyst turnover. This transformation is the first in which a ZrCl4 ⋅BINOL complex serves as a chiral Lewis-acid-assisted Brønsted acid.
A conjugate addition/asymmetric protonation/aza-Prins cascade reaction has been developed for the enantioselective synthesis of fused n class="Chemical">polycyclic indolines. A catalyst system generated from ZrCl4 and 3,3'-dibromo-BINOL enables the synthesis of a range of polycyclic indolines in good yields and with high enantioselectivity. A key finding is the use of TMSCl and 2,6-dibromophenol as a stoichiometric source of HCl to facilitate catalyst turnover. This transformation is the first in which a ZrCl4 ⋅BINOL complex serves as a chiral Lewis-acid-assisted Brønsted acid.
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