Solvent-free reactions of alkynes in ball mills: It is definitely more than mixing

Abstract

This contribution presents two solvent-free reactions of terminal alkynes in ball mills: Pd-catalyzed Sonogashira cross-coupling and Cu-catalyzed homo-coupling (Glaser reaction). The results are compared to other solvent-free reaction protocols, which have been published up to date for those types of reactions. Reactions are assessed on the basis of reaction variables like type of catalyst and base or reaction time. Furthermore, performance-based parameters (yield, selectivity, turnover number, TON, and turnover frequency, TOF) are considered and evaluated. Findings from ball-milling experiments indicate that those processes are comparable to the energy entry by microwave irradiation with respect to reaction time and TOF. © 2011, IUPAC.