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Updated: Sep 25, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Diastereoselective additions of nucleophiles to alpha-acetoxy ethers using the alpha-(trimethylsilyl)benzyl auxiliary
Scott D Rychnovsky1, Jennifer Cossrow
1Department of Chemistry, 516 Rowland Hall, University of California-Irvine, Irvine, CA 92697-2025, USA. srychnov@uci.edu
Abstract:
We report the diastereoselective addition of a variety of nucleophiles to alpha-(trimethylsilyl)benzyl-substituted oxocarbenium ions. The oxocarbenium ions are generated from alpha-acetoxy ethers, which are easily prepared via reductive acetylation of esters. The alpha-(trimethylsilyl)benzyl auxiliary produces good to excellent facial selectivity with a variety of nucleophiles, including silyl enol ethers, silyl ketene acetals, allylsilanes, and crotylsilanes. The utility of this auxiliary is further demonstrated in a complex ketone aldol coupling reaction. [reaction: see text]
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