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Updated: Mar 26, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Direct conjugate alkylation of α,β-unsaturated carbonyls by Ti(III)-catalysed reductive umpolung of simple activated
Plamen Bichovski1, Thomas M Haas1, Manfred Keller1
1Institut für Organische Chemie, Albert-Ludwigs-Universität Freiburg, Albertsraße 21, 79104 Freiburg, Germany. jan.streuff@ocbc.uni-freiburg.de.
Abstract:
The titanium(iii)-catalysed cross-selective reductive umpolung of Michael-acceptors represents a unique direct conjugate β-alkylation reaction. It allows the cross-selective preparation of 1,6- and 1,4-difunctionalised building blocks without the requirement of stoichiometric organometallic reagents. In this full paper, the development and scope of the titanium(iii)-catalysed cross-selective reductive umpolung of Michael-acceptors is described. Based on the observed selectivities and additional mechanistic experiments a refined mechanistic proposal is presented.
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