Fluorochemicals from fluorspar via a phosphate-enabled mechanochemical process that bypasses HF

Abstract

All fluorochemicals—including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents—are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF 2 ) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF 2 . Inspired by calcium phosphate biomineralization, we herein disclose a protocol of treating acid-grade fluorspar with dipotassium hydrogen phosphate (K 2 HPO 4 ) under mechanochemical conditions. The process affords a solid composed of crystalline K 3 (HPO 4 )F and K 2− x Ca y (PO 3 F) a (PO 4 ) b , which is found suitable for forging sulfur-fluorine and carbon-fluorine bonds.

Batch and continuous flow mechanochemical synthesis of organic compounds including APIs

“…the correct reaction mechanism and subsequently the reaction kinetics will be key for the design of mechanochemical reactors as the Arrhenius approach of defining the rate constant may or may not hold. b) Uncharted reactions: a recent wok by Patel et al 75 reports the use of CaF as an excellent fluorinating agent when used in solvent-free environments at much milder conditions and over a wide range of substrates. Such efforts will help new reactions to be explored in a rather more selective manner.…”

“…b) Uncharted reactions: a recent wok by Patel et al 75 reports the use of CaF as an excellent fluorinating agent when used in solvent-free environments at much milder conditions and over a wide range of substrates. Such efforts will help new reactions to be explored in a rather more selective manner.…”

Main group metal-mediated strategies for C–H and C–F bond activation and functionalisation of fluoroarenes

“…3 The synthesis of uoroarenes usually involves the highly toxic and corrosive gas hydrogen uoride (HF), however Aldridge and Gouverneur have recently developed a new method to access uorochemicals via a mechanochemical process involving acid grade uorspar (>97% CaF 2 ) and dipotassium hydrogen phosphate (K 2 HPO 4 ) by-passing the formation of HF offering a safer approach to the synthesis of these important compounds. 4 The development of methods for the regioselective functionalisation of C-H and C-F bonds in these molecules is highly sought for in synthesis.…”

Mechanochemical difluoromethylation of (thio)phenols and N‐heterocycles

“…[2,5] These unique advantages have prompted groups around the world, including our own, to embrace mechanochemistry to provide solutions to synthetic challenges with the prospect of global societal benefits. [1,[13][14][15][16][17] The popularity of CF 2 H compounds has grown exponentially throughout the last decade. This trend has directly sparked the development of new methods for the preparation of CF 2 H compounds.…”