Migratory Functionalization of Unactivated Alkyl Bromides for Construction of all-Carbon Quaternary Centers via Transposed tert-C-Radicals
Chao Feng and Patrick Walsh describe the construction of all-carbon quaternary centers via transposed tert-C-radicals.
All-carbon quaternary centers are ubiquitous in natural products and pharmaceuticals, as well as functional materials. According to Professor Chao Feng from Nanjing Tech University, P. R. of China, “tertiary C−C cross-coupling conceptually constitutes one of the most concise and straightforward approaches to access the three-dimension spread structures. However, the apparent steric repulsion and hydride elimination severely impede the development of this strategy. Established protocols have focused mainly on functionalization of tertiary alkyl nucleophiles or electrophiles but limited functional groups or coupling partners can typically be used. Furthermore, the unwanted regioisomers deriving from isomerization of the metallic tert-alkyl intermediate were often obtained, together with the target product. Therefore, developing general methods for novel types of C–C bond formation at the sterically demanding tertiary carbons from easily available starting materials is highly appealing.” Recently, a collaborative effort between the group of Professor Feng and that of Professor Patrick J. Walsh from the University of Pennsylvania, USA, uncovered a way of constructing all-carbon quaternary-center-embedded frameworks from unactivated primary/secondary alkyl bromides via a NiH-engaged chain walking event.