Trifluorotoluene

Synthesis

For small-scale laboratory preparations, trifluorotoluene is synthesized by coupling an aromatic halide and trifluoromethyl iodide in the presence of a copper catalyst:

For large scale preparations using batch or continuous processes, benzotrichloride is treated with hydrogen fluoride under pressure.

Uses

Trifluorotoluene has a variety of niche uses.

Solvent alternative to dichloromethane

According to Ogawa and Curran, trifluorotoluene is similar to dichloromethane in standard acylation, tosylation, and silylation reactions. The dielectric constants for dichloromethane and trifluorotoluene are 9.04 and 9.18, respectively, indicating similar solvating properties. Dipole moments compare less favorably: 1.89 and 2.86 D for dichloromethane and trifluorotoluene, respectively. Replacing dichloromethane is advantageous when conditions require higher boiling solvents since trifluorotoluene boils 62 °C higher than dichloromethane (b.p. 40 °C).

As a solvent, trifluorotoluene is useful in mild Lewis-acid catalyzed reactions, such as the Friedel-Crafts preparations. The most common catalyst, aluminium trichloride reacts with trifluorotoluene at room temperature; however, zinc chloride does not.

Synthetic intermediate

A second and perhaps more valuable use of trifluorotoluene is as a synthetic intermediate. A derivative of trifluorotoluene, 3-aminobenzotrifluoride, is the precursor to the herbicide fluometuron. It is synthesized via nitration followed by reduction to meta-H₂NC₆H₄CF₃. This aniline is then converted to the urea.

Flumetramide (6-[4-(trifluoromethyl)phenyl]morpholin-3-one), a skeletal muscle relaxant, is also prepared from trifluorotoluene.