Copper-Catalyzed Decarboxylative Trifluoromethylation Reactions

Abstract

Trifluoromethanes play an important role in medicinal chemistry, and methods that enable the rapid synthesis of trifluoromethanes from common functional groups are essential for the synthesis of bioactive compounds. We describe a series of Cu-catalyzed decarboxylative trifluoromethylation reactions that enable the conversion of alcohols to trifluoromethanes. These reactions rely on the efficient generation of nucleophilic “Cu–CF3”, and Chapter 1 provides background on the synthesis, stability, and reactivity of this organometallic species. In addition, we discuss the use of halodifluoroacetates as common, inexpensive, and green precursors to “Cu–CF3”. Cu-catalyzed trifluoromethylation of electrophiles was an appealing, but underdeveloped strategy for accessing fluorinated compounds. Chapter 2 describes our entry into Cu-catalyzed decarboxylative trifluoromethylation of bromodifluoroacetates. We discovered that ligand and catalyst activation played critical roles in the development of an efficient Cu-based catalyst system. Trifluoroethylarenes are commonly found in bioactive compounds, and in Chapter 3, we describe a straightforward Cu-catalyzed strategy to access this motif from benzylic bromodifluoroacetates. A key aspect of this reaction involved the generation of active electrophilic species in situ. In Chapter 4, we describe the ability of ligands to alter the regioselectivity of Cu-catalyzed trifluoromethylation reactions. Propargylic bromodifluoroacetates are converted into a mixture of propargylic trifluoromethanes and trifluoromethylallenes using “Cu–CF3”; however, the use of 1,10-phenanthroline inverts the typical regioselectivity, and provides trifluoromethylallenes in high yield and selectivity. This is the first example of ligands controlling the regioselectivity of Cu-based trifluoromethylation reactions.