Diastereodivergent and Enantioselective Access to Spiroepoxides via Organocatalytic Epoxidation of Unsaturated Pyrazolones

Published on 2017-09-14T14:33:18Z (GMT) by
Readily available chiral amine–thioureas are effective catalysts for the first diastereo- and enantioselective epoxidation of unsaturated pyrazolones. The <i>trans</i>- or <i>cis</i>-spiroepoxides are preferentially obtained in good yield and high to excellent enantioselectivity using an appropriate organocatalyst and <i>tert</i>-butyl hydroperoxide as the oxidant. The epoxidation appears applicable to highly challenging β,β′-substituted unsaturated pyrazolones, giving access to spiroepoxides bearing two vicinal quaternary stereocenters. The reaction represents a unique example of Weitz–Scheffer epoxidation, where the catalyst-controlled ring-closure step is usefully exploited to prepare both enantioenriched diastereomeric epoxides.

Cite this collection

Meninno, Sara; Roselli, Angelo; Capobianco, Amedeo; Overgaard, Jacob; Lattanzi, Alessandra (2017): Diastereodivergent and Enantioselective Access to

Spiroepoxides via Organocatalytic Epoxidation of Unsaturated Pyrazolones. ACS Publications.

https://doi.org/10.1021/acs.orglett.7b02189

Retrieved: 00:01, Nov 24, 2017 (GMT)