The Mizoroki-Heck reaction in mesoionic 1-butyl-3-methyltetrazolium-5-olate

1-Butyl-3-methyltetrazolium-5-olate (1), a mesoionic compound, exists as a liquid at room temperature and can be used as a polar solvent for the Mizoroki-Heck reaction, wherein it has been proven to be a superior solvent to other solvents. The reaction of iodobenzene with ethyl acrylate in the presence of palladium acetate in mesoionic liquid 1 at 40 degrees C for 24 h gave ethyl cinnamate in 78% yield in the absence of ligands, while the use of other solvents, such as [bmim][BF4], [bmim][PF6], and DMF gave lower yields (43%, 37%, and 17%, respectively) under the same conditions. Heck-type coupling reactions of electron-deficient or electron-rich aryl iodides and bromobenzenes with olefins (15 examples, 7%-97%) were performed in 1. When a phosphine ligand was added to the reaction mixture, aryl bromides could be used, and the mesoionic liquid containing the catalysts could be reused at least five times. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Compound 1, a mesoionic compound, serves as a superior solvent for the Mizoroki-Heck reaction, yielding high product yield without the need for ligands. Various Heck-type coupling reactions were successfully performed in mesoionic liquid 1, and the catalysts could be reused multiple times with the addition of a phosphine ligand.