A highly diastereo- and enantioselective [3 + 3] annulation of donor–acceptor cyclopropanes with mercaptoacetaldehyde has been developed. In the presence of a N,N′-dioxide–Sc(III) complex as the catalyst, a number of aromatic substituted cyclopropyl ketones reacted with mercaptoacetaldehyde smoothly, providing the corresponding chiral tetrahydrothiopyranols in moderate yields with excellent ee (up to 99% ee) and dr values (up to >19 : 1).