Synthesis of Spirocyclic Compounds by a Ring-Expansion/Cationic Cyclization Cascade Reaction of Chlorosulfate Derivatives.

A novel cascade reaction to prepare spirocarbocyclic compounds from chlorosulfate derivatives has been developed. The process involves an unusual thermal elimination of the chlorosulfate moiety, a ring-expansion reaction, and a subsequent cationic cyclization reaction. Despite the relatively complex skeletal rearrangement, the reaction described here is featured by its operational simplicity, being just a thermal process that does not require additional reagents, catalysts, or additives.