Diastereoselective bromodifluoromethylation and difluoromethylation of chiral imide enolates via insertion of difluorocarbene

A Unified Strategy for the Synthesis of Difluoromethyl- and Vinylfluoride-Containing Scaffolds

Here, we report a general method for the synthesis of quaternary and tertiary difluoromethylated compounds and their vinylfluoride analogues. The strategy, which relies on a two-step sequence featuring a C-selective electrophilic difluoromethylation and either a palladium-catalyzed decarboxylative protonation or a Krapcho decarboxylation, is practical, scalable, and high yielding. Considering the generality of the method and the attractive properties offered by the difluoromethyl group, this approach provides a valuable tool for late-stage functionalization and drug development.

Introduction of fluorine and fluorine-containing functional groups

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.

Polarity-mismatched addition of electrophilic carbon radicals to an electron-deficient acceptor: cascade radical addition-cyclization-trapping reaction

The polarity-mismatched perfluoroalkyl radical addition to electron-deficient alkenes was studied. For this study, several substrates having two polarity-different radical acceptors were employed to investigate the regiochemical courses of cascade reaction. In the case of substrate 1 having a methacryloyl moiety, we found polarity-mismatched perfluoroalkylation giving 15a-e as a major course over the polarity-matched perfluoroalkylation giving 16a-e. Moreover, in the case of substrates 2-7, perfluoroalkyl radicals selectively added to an electron-deficient alkene moiety of 2-7, to give polarity-mismatched perfluoroalkylation products without the formation of regioisomers. Next, the control of enantioselectivity was studied. In the case of substrates 1 and 3, the reaction proceeded with good enantioselectivities by employing a chiral Lewis acid, prepared from chiral box ligand 24 and Zn(OTf)(2). For direct comparison, we also studied the reaction with other carbon radicals, derived from ICH(2)CO(2)Et, ICH(2)CN, BrC(CO(2)Et)(2)Me, and CCl(3)Br, which have electrophilic character.