Abstract

Trifluoromethylated building blocks and intermediates are in exceptionally high demand for the synthesis of agrochemicals, pharmaceuticals, and specialty materials. Readily available, nontoxic and ozone-friendly fluoroform (CHF₃, trifluoromethane, HFC-23), a side-product of Teflon manufacturing and a potent greenhouse gas, would be by far the best CF₃ source for a variety of trifluoromethylation reactions. Chemoselective activation of fluoroform, however, is highly challenging. This article provides an overview of synthetic methods employing fluoroform with emphasis on new trends and most recent, promising developments in the area.

INTRODUCTION

In its April 3, 1890 issue, the Nature magazine highlighted (1) two papers on the same subject presented at the then most recent meeting of the Chemical Society of Paris. The topic was the isolation of fluoroform, CHF₃, the last member of the haloform family to be discovered, by Chabrié and Meslans. Both scientists had prepared and isolated fluoroform from the reactions of chloroform or iodoform with silver fluoride, determined its density, and probed its alkaline hydrolysis (1-4). Since then, however, fluoroform had remained an exotic and virtually unstudied compound for over 40 years (5) until in the mid-1930s Ruff (6) and Henne (7) developed the synthesis of fluoroform from HgF and CHI₃ or CHF₂Br, respectively. These methods enabled, for the first time, the preparation of pure fluoroform in sufficient quantities for thorough reactivity and biological activity studies. The results of those studies by Henne led him to identify fluoroform as a “substance characterized by exceptional physiological and chemical inertness” (7). In his 1937 report, Henne wrote:

“Fluoroform is character ... ...