Pauson-Khand Reaction of Internal Dissymmetric Trifluoromethyl Alkynes. Influence of the Alkene on the Regioselectivity

Over the past decade, the most significant, conceptual advances in the field of fluorination were enabled most prominently by organo- and transition-metal catalysis. The most challenging transformation remains the formation of the parent C-F bond, primarily as a consequence of the high hydration energy of fluoride, strong metal-fluorine bonds, and highly polarized bonds to fluorine. Most fluorination reactions still lack generality, predictability, and cost-efficiency. Despite all current limitations, modern fluorination methods have made fluorinated molecules more readily available than ever before and have begun to have an impact on research areas that do not require large amounts of material, such as drug discovery and positron emission tomography. This Review gives a brief summary of conventional fluorination reactions, including those reactions that introduce fluorinated functional groups, and focuses on modern developments in the field. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An efficient copper-mediated trifluoromethylation of terminal alkynes with nucleophilic trifluoromethylating reagent (Me(3)SiCF(3)) was developed. Both aromatic alkynes and aliphatic alkynes were effective, and a variety of functionalities such as amino, -OMe, -CO(2)Et, -Br, and -NO(2) were tolerated under the reaction conditions. This reaction provides a general, straightforward, and practically useful method to prepare trifluoromethylated acetylenes.