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Updated: Jul 4, 2026

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Cobalt-Stabilized Propargylic Oxocarbenium Ions Enable Direct and Asymmetric Nickel(II) Catalyzed Aldol-Like
Xènia Tarrach1, Leah O'Neill1, Anna M Costa1
1Department of Inorganic and Organic Chemistry, Section of Organic Chemistry, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona, Carrer Martí i Franqués 1, 08028 Barcelona, Catalonia, Spain.
Abstract:
We describe a direct and asymmetric aldol-like reaction between a wide range of N-acyl-1,3-oxazolidine-2-thiones and cobalt-protected propargylic acetals catalyzed by a chiral nickel(II) complex leading to syn β-alkoxy derivatives. This overcomes longstanding limitations associated with acetals from aliphatic aldehydes, selectively providing syn aldol adducts in excellent yields as single stereoisomers (dr >97:3, er up to >99:1). Furthermore, the cobalt fragment enables downstream intramolecular Pauson-Khand cyclizations, granting rapid access to densely functionalized bicyclic architectures.
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One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
α-Alkylation of Ketones via Enolate Ions

