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

Abstract

The synthesis of small rings by functionalization of C(sp 3 ) À Hb onds remains ag reat challenge.W er eport for the first time ac opper-catalyzed [1+ +1+ +1] cyclotrimerization of acetophenone derivatives under mild reaction conditions.T he reaction has ab road scope for the stereoselective synthesis of cyclopropanes by trimerization of acetophenone.T he developed transformation is based on an extraordinary coppercatalyzedcascade process that allows saturated carbocycles to be obtained for the first time by cyclotrimerization through functionalization of C(sp 3 ) À Hb onds.T he cascade of sixfold C(sp 3 )ÀHb ond functionalization allows the synthesis of cyclopropanes in ahighly stereoselective approach.