Dearomatization Reactions of N-OMe Ureas

In an attempt to control chemoselectivity in the dearomatization reactions of benzylic ureas, the corresponding <i>N</i>-methoxy ureas were evaluated as stabilized nitrenium ion equivalents. Substrates derived from secondary amines undergo cyclization upon treatment with iodosobenzene diacetate to afford the corresponding spirocyclic ureas in modest to excellent yield. The scope and limitations of this transformation are reported. In addition, some reactions of the dearomatized product are described, resulting in the construction of fragments of the marine alkaloid KB343.