Copper‐Catalyzed [3+2] Cycloaddition and Interrupted Fischer Indolization to Prepare Polycyclic Furo[2,3‐b]indolines from N ‐Aryl Isatin Nitrones and Methylenecyclopropanes

Various polycyclic furo[2,3‐b]indolines containing a cyclopropane ring have been prepared in moderate yields with high diastereoselectivity from N ‐aryl isatin nitrones and methylenecyclopropanes using a copper‐catalyzed [3+2] cycloaddition and subsequent interrupted Fischer indolization strategy under mild reaction conditions. The obtained furo[2,3‐b]indolines were easily converted to piperidinone‐fused furo[2,3‐b]indolines by selective [1,3]‐rearrangement through N−O bond cleavage. Finally, two chiral polycyclic furo[2,3‐b]indolines were obtained by chiral auxiliary control.