[1+1+1] Cyclotrimerization for the Synthesis of Cyclopropanes

摘要

The synthesis of small rings by functionalization of C(sp(3))-H bonds remains a great challenge. We report for the first time a copper-catalyzed [1+1+1] cyclotrimerization of acetophenone derivatives under mild reaction conditions. The reaction has a broad scope for the stereoselective synthesis of cyclopropanes by trimerization of acetophenone. The developed transformation is based on an extraordinary copper-catalyzed cascade process that allows saturated carbocycles to be obtained for the first time by cyclotrimerization through functionalization of C(sp(3))-H bonds. The cascade of sixfold C(sp(3))-H bond functionalization allows the synthesis of cyclopropanes in a highly stereoselective approach.