General, Robust, and Stereocomplementary Preparation of β-Ketoester Enol Tosylates as Cross-Coupling Partners Utilizing TsCl−N-Methylimidazole Agents

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Abstract

We have developed a general, robust, and cost-effective method for the (E)- or (Z)-stereocomplementary enol tosylation of β-ketoesters using TsCl−N-methylimidazole (NMI)−Et₃N or LiOH. TsCl coupled with NMI formed a highly reactive N-sulfonylammonium intermediate. Stereocongested secondary alcohols were smoothly sulfonylated using Ts(Ms)Cl−NMI−Et₃N. β-Ketoesters underwent (E)-selective tosylation using TsCl−NMI−Et₃N and (Z)-selective tosylation using TsCl−NMI−LiOH (total of 23 examples; 60%−99% yield). Stereoretentive Negishi and Sonogashira couplings using enol tosylates proceeded successfully to give trisubstituted α,β-unsaturated esters.

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This article has been cited by 6 ACS Journal articles (5 most recent appear below).

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