Solid-phase synthesis of bis(guanidines) based on an aza Wittig/carbodiimide-mediated annulation process

An efficient solid-phase synthetic method towards bis(guanidines) is report ed via aza Wittig coupling of a solid-supported bis(iminophosphorane) with an aromatic isothiocyanate to generate the corresponding solid-supported im inophosphorane, which upon exposure to a second aromatic isothiocyanate und erwent aza Wittig/intramolecular cyclization and simultaneous cleavage to g ive the desired bis(guanidines).