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Updated: Jul 18, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Short, enantioselective total synthesis of aflatoxin B2 using an asymmetric [3+2]-cycloaddition step
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Abstract:
A highly enantioselective [3+2]-cycloaddition reaction of 2,3-dihydrofuran with 1,4-benzoquinones using a chiral oxazaborolidinium triflimidate as catalyst has been developed which allows rapid access to a variety of chiral phenolic tricycles (enantiomeric excesses ranging from 91 to 98%). The utility of this new methodology is demonstrated by a short synthesis of the important pentacyclic natural product, aflatoxin B2. This exploratory study indicates that an even broader application of these catalysts to enantioselective cycloadditions may be possible.
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