Exploring hydroamination-cycloaddition-fragmentation sequences to access polycyclicguanidines and vinyl-2-aminoimidazoles.

These substrates undergo [4+2]-cycloaddition reactions to generate a series of complex cyclic- and spirocyclic-guanidines. Select substrates can further undergo a ring opening-elimination cascade that ultimately reveals a vinyl-2-aminoimidazole. As such this cascade reaction may find application in the synthesis of oroidin-type natural products and their analogues.