Yb(OTf) 3 -Catalyzed Formal (4 + 3) Cycloaddition Reactions of 3-Benzylideneindoline-2-thiones with Donor-Acceptor Cyclopropanes.

A Yb(OTf)-catalyzed formal (4 + 3) cycloaddition reaction of donor-acceptor cyclopropanes with 3-benzylideneindoline-2-thiones as sulfur-containing 4π components has been successfully achieved. A series of functionalized 5,10-dihydro-2-thiepino[2,3-]indole derivatives were synthesized with good yields and moderate to good diastereoselectivity. The reaction described herein represented the inaugural (4 + 3) cycloaddition of 3-benzylideneindoline-2-thiones.