Regioselective 5-exo-dig (halo)cyclization of N-propargyloxycarbonyl guanidine derivatives under mild conditions

A highly regioselective 5-exo-dig cyclization of aromatic N-propargyloxycarbonyl guanidines was developed via an Ag(i)-catalyzed intramolecular hydroamination reaction. This method features a fast reaction rate and mild reaction conditions. Furthermore, it was extended to access halogenated analogues via a one-pot Ag(i)-catalyzed bromocyclization reaction or an I-2-mediated iodocyclization reaction with high E/Z selectivity.