Ketenedithioacetals as Surrogates for the Formal Insertion of Ketenes into Donor–Acceptor Cyclopropanes

The reactivity of donor–acceptor (D–A) cyclopropanes towards acceptor‐substituted ketenedithioacetals was investigated. In a Lewis‐acid‐catalyzed (3+2)‐cycloaddition, the corresponding dithiaspiro compounds were synthesized in good yields. The 1,3‐dithiane unit, a masked keto functionality, was cleaved by N ‐iodosuccinimide. Thus, this two‐step process represents a formal insertion of an acceptor‐substituted ketene into a D–A...