Stereoselective Approach to Multisubstituted Enolates from Unactivated Alkynes: Oxyalkylidenation of Alkynyl Ketone Enolates with Aldehydes

S. Sasaki, J. Kikuchi,* S. Ito, N. Yoshikai*
J. Org. Chem. 2023, 88, 14096–14104. DOI: 10.1021/acs.joc.3c01615

Abstract: The preparation of multisubstituted enolates with precise regio- and stereocontrol is a nontrivial task when using conventional deprotonation methods on the corresponding carbonyl compounds. We describe herein an approach to preparing stereodefined enolates by leveraging the stereoselective oxyfunctionalization of unactivated alkynes, particularly in the context of alkynylogous aldol reaction. trans-Iodo(III)acetoxylation of alkynes and subsequent Sonogashira coupling allow for facile preparation of multisubstituted enynyl acetates, which can be deacetylated by MeLi into the corresponding enolates. The alkynyl enolates react with aldehydes to afford γ,δ-unsaturated β-diketones through a cascade of alkynylogous aldol addition, intramolecular Michael addition, and ring opening of the oxetene intermediate.

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