Silica gel promoted environment-friendly synthesis of α-amino amidines and regioselective transformation of α-amino amidines into amidino substituted indazoles

Environment-friendly three-component Ugi-type strategy (U-3CR) for the synthesis of a wide variety of α-amino amidines has been developed by using silica gel as promoter, and a novel access to amidino substituted indazoles in a regioselective manner is presented via iron(III) catalyzed post Ugi cyclization strategy. This method allows an easy construction of amidino substituted indazoles in good yields with broad substrate scope starting from readily available starting materials.