A general method for nearly reduction-free dehalogenations in a fluorinated biphasic system

We have studied the dehalogenations of halofluorinated alkanes and fluorinated ethers, both linear and cyclic, as well as halofluorinated alkanes containing an aromatic moiety, to their corresponding unsaturated species in a biphase fluorinated/hydrogenated solvent system.The reactions in the biphase system lead to higher selectivities and better yields than those obtained performing the reaction in the traditional hydrogenated monophasic system. By this method, the concentrations of hydrogenated by-products of general formula R–CF2H or RCFHR’ are as low as 100 ppm.This novel biphasic system provides therefore a useful synthetic route to materials and chemicals for electronics, optical polymers, plasma etching, etc. which require a very high purity of all compounds involved.

A modified version of the fluorinated biphase system in the Zn-mediated dehalogenations of compounds 1–3 and 7, in the presence of a fluorinated solvent and a hydrogenated co-solvent affords as much as a 7-fold decrease in hydrogenated by-products with high yields with respect to the classical homogeneous Zn-based dehalogenation that employs solely a hydrogenated solvent. Figure optionsDownload as PowerPoint slide