title: Fast, ligand- and solvent-free synthesis of 1,4-substituted buta-1,3-diynes by Cu-catalyzed homocoupling of terminal alkynes in a ball mill.
abstract: A method for the Glaser coupling reaction of alkynes by using a vibration ball mill has been developed. The procedure avoids the use of ligands and solvents during the reaction. Aryl- and alkyl-substituted terminal alkynes undergo homocoupling if coground with KF-Al(2)O(3) and CuI as a milling auxiliary and catalyst. Furthermore, an alternative protocol has been developed incorporating 1,4-diazabicyclo[2.2.2]octane (DABCO) as an additional base allowing the use of KF-Al(2)O(3) with a lower KF loading. Besides Cu salts, the homocoupling of phenylacetylene is also catalyzed by Ni or Co salts, as well as by PdCl(2). TMS-protected phenylacetylene could be directly converted into the homocoupling product after in situ deprotection of the alkyne by fluoride-initiated removal of the trimethylsilyl group.
authors.affiliation: Institute for Technical Chemistry and Environmental Chemistry, Friedrich-Schiller University Jena, Lessingstrasse 12, 07743 Jena, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Schmidt
authors.forename: Rico
authors.initials: R
authors.lastname: Thorwirth
authors.forename: Tony
authors.initials: T
authors.lastname: Szuppa
authors.forename: Achim
authors.initials: A
authors.lastname: Stolle
authors.forename: Bernd
authors.initials: B
authors.lastname: Ondruschka
authors.forename: Henning
authors.initials: H
authors.lastname: Hopf