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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Electroreductive intramolecular coupling of aromatic imino esters: is four-membered cyclization much more favorable
Naoki Kise1, Yuuki Hirano, Yoshi Tanaka
1Department of Biotechnology, Faculty of Engineering, Tottori University, Koyama, Tottori 680-8552, Japan. kise@bio.tottori-u.ac.jp
Abstract:
[reaction: see text] The electroreduction of an aromatic imino ester prepared from (S)-glutamic acid in the presence of chlorotrimethylsilane and triethylamine afforded a four-membered cyclized product, a mixed ketal of cis-2,4-disubstituted azetidine-3-one, stereospecifically. Calculations for the transition states by the DFT method support the predominant formation of the azetidine. The electroreduction of an aromatic imino ester prepared from (S)-aspartic acid gave almost equal amounts of a diastereomerically pure mixed ketal of cis-2,4-disubstituted azetidine-3-one and a diastereomeric mixture of 2,5-disubstituted pyrollidine-3-one.
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