Silver acetate-catalyzed synthesis of cyclic sulfonyl guanidine with exocyclic double bond

An efficient protocol for the synthesis of cyclic guanidine with exocyclic double bond has been developed. The synthesis has been achieved via intramolecular hydroamination of an intermediate propargyl guanidine by using silver acetate as catalyst in the presence of acetic acid. The reaction proceeds via the formation of acyclic propargyl guanidine in a one-pot reaction of N,N -dibromoarylsulfonamides, isonitriles, and propargylamine in the presence of K 2 CO 3 . In the second stage of the synthesis, the acyclic guanidine selectively undergoes 5- exo -dig cyclization in the presence of silver acetate and acetic acid to produce the five-membered cyclic guanidine framework having an exocyclic double bond as the constituent part. Short reaction time, wide substrate scope with good to high yields, and good functional group tolerance are the remarkable achievement of the present protocol. Graphical abstract