Controlled Synthesis of 1,3,5-Oxadiazin-2-ones and Oxazolones through Regioselective Iodocyclization of Ynamides

Two efficient processes based on the iodocyclization of ynamides have been developed: (i) N-alkynyl tert-butyloxycarbamates were found to undergo a rare 6-exo-dig ring closure reaction affording 1,3,5-oxadiazin-2-ones by using acetonitrile as solvent; (ii) In the absence of acetonitrile, N-alkynyl tert-butyloxycarbamates could undergo 5-endo-dig cyclization providing oxazolones.