Intermolecular Coupling of Alkenes to Heterocycles via C−H Bond Activation

The intermolecular coupling of unactivated alkenes to a range of heterocycles using a Rh(I) catalyst was investigated. A variety of functional groups were incorporated into the alkene, including esters, nitriles, acetals, and phthalimide. Furthermore, the heterocycle tolerated substitution with both electron-rich and electron-deficient groups. The intermolecular coupling became possible after it was discovered that weak acids dramatically increase the rate of both the inter- and intramolecular reactions. An extensive optimization of additives was performed, and HCl·PCy3 (Cy = cyclohexyl) and HCl·P-t-Bu2Et were in general found to be the best additives for the reaction.