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.