1. While the size of the methyl and trifluoromethyl group is comparable, the latter possesses a strong electron-withdrawing effect. Therefore, the replacement of a CH3 group by a CF3 group in a molecule results in a great change of its electronic properties and reactivity. The trifluoromethyl group of drugs plays an important role in drug–receptor interactions and in the in vivo transport. In addition, the high chemical and biological stability of the CF3 group allows to avoid unwanted metabolic transformations. For reviews, see:
2. Fluorine in Bioorganic Chemistry,1993
3. Fluorine Containing Drugs in Organofluorine Chemicals and their Industrial Application;Filler,1979
4. Chemistry of Organic Compounds;Hudlicky,1992
5. First dual NK1 antagonists–serotonin reuptake inhibitors: synthesis and SAR of a new class of potential antidepressants