Abstract
A new approach is described for the synthesis of spiro[piperidine-3,2'-oxindoles] in 35-82 yields with excellent stereoselectivity via the [4 + 2] cycloaddition reaction of donor-acceptor cyclobutanes with iminooxindoles in the presence of 10-30 mol% Sc(OTf)(3) at room temperature. This methodology provides great potential for building spiro-heterocycle compounds from simple building blocks.