(2-Fluoroallyl)boration of Ketones with (2-Fluoroallyl)boronates

Efficient routes toward activation of gem-chlorofluorocyclopropane-derived (2-fluoroallyl)­boronates for allylboration of various ketones including functionalized and low-reactive ones were developed. Increasing the boron electrophilicity by the transformation of a boronate moiety into a borinic ester with nBuLi/trifluoroacetic anhydride (TFAA) makes (2-fluoroallyl)­boration of acetyl arenes/hetarenes and aliphatic ketones possible with high diastereoselectivity. For low-reactive or sterically hindered ketones (e.g., benzophenone, adamantanone), “CuF”-based catalysts were developed: (NHC)­CuF·HF and (NHC)­CuOTf in the presence of an excess of KHF2 (NHC = IPr, SIPr, IPrCl).