Metal-Free Intermolecular Allylic C-H Amination of Alkenes Using Primary Carbamates

The allylic C-H amination of alkenes is a powerful method for the regioselective formation of new C-N bonds. Though many methods for introducing a wide range of nitrogen groups intermolecularly have been developed, few of these utilize carbamates, which are an important class of bioactive compounds and are commonly used as protecting groups for free amines. Here, we report a convenient metal-free protocol for intermolecular allylic C-H amination using unactivated primary carbamates as the nitrogen source. A sterically hindered NHC-selenium catalyst was found to be critical to obtaining high yields. A wide range of trisubstituted and 1,1-disubstituted alkenes were regioselectively aminated, including terpenoid natural products. A range of common carbamate-protecting groups such as Cbz, Teoc, and Alloc could be successfully incorporated into alkene substrates. Additionally, trifluoroacetamide was shown to be a viable nitrogen source. The observed regio-and stereoselectivities can be explained by a sequential ene reaction/[2,3]-sigmatropic rearrangement mechanism in which cis C-H bonds are preferentially activated, but subsequent rearrangement results in selective formation of trans alkene products.