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Updated: Mar 16, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Alkaloid-Catalyzed Enantioselective [3 + 2] Cycloaddition of Ketenes and Azomethine Imines
Mukulesh Mondal1, Kraig A Wheeler2, Nessan J Kerrigan1
1Department of Chemistry, Oakland University , 2200 North Squirrel Road, Rochester, Michigan 48309-4477, United States.
Abstract:
A new asymmetric synthesis of bicyclic pyrazolidinones through an alkaloid-catalyzed formal [3 + 2] cycloaddition of in situ generated ketenes and azomethine imines is described. The products were formed in good to excellent yields (52-99% for 17 examples), with good to excellent diastereoselectivity (dr 5:1 to 27:1 for 11 examples), and with excellent enantioselectivity in all cases (≥96% ee). This method represents the first unambiguous example of an enantioselective reaction between ketenes and a 1,3-dipole.
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