Urea-Catalyzed Functionalization of Unactivated C–H Bonds

Abstract

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

Urea-Catalyzed Vinyl Carbocation Formation Enables Mild Functionalization of Unactivated C–H Bonds

“…In conclusion, we disclose a novel application of hydrogenbonding scaffolds, where 3,5-bistrifluoromethylphenyl ureas catalyze C−C bond-forming reactions of vinyl triflates under strongly basic conditions. 18 In the presence of these catalysts, the proposed reactive dicoordinate carbocation intermediates undergo facile C−H insertion and Friedel−Crafts reactions in good to excellent yield. This strategy demonstrates the utility of vinyl carbocation reactions and introduces easily accessible and modular catalysts for these transformations.…”