title: General, robust, and stereocomplementary preparation of beta-ketoester enol tosylates as cross-coupling partners utilizing TsCl-N-methylimidazole agents.
abstract: We have developed a general, robust, and cost-effective method for the (E)- or (Z)-stereocomplementary enol tosylation of beta-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. beta-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 alpha,beta-unsaturated esters.
authors.affiliation: Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo, Japan.
authors.forename: Hidefumi
authors.initials: H
authors.lastname: Nakatsuji
authors.forename: Kanako
authors.initials: K
authors.lastname: Ueno
authors.forename: Tomonori
authors.initials: T
authors.lastname: Misaki
authors.forename: Yoo
authors.initials: Y
authors.lastname: Tanabe