Utility of Ammonium Salts for the Synthesis of Amidines

Significance

Reported is a copper-catalyzed, three-component coupling reaction of terminal alkynes, sulfonyl or phosphoryl azides and ammonium salts to give N-unprotected amidines. The derived amidines with a 2-bromosulfonyl moiety were efficiently cyclized by a copper-catalyzed ­intramolecular arylation to afford 2H-1,2,4-benzo-thiadiazine-1,1-dioxides. The reaction is carried out under very mild (room temperature), simple (inert atmosphere is not required) conditions using inexpensive ammonium salt or aqueous ammonia reagents. The synthesis of amidines proceeds mostly in good yields, except for using a phosphoryl azide (39% yield). The cyclization also proceeds in good yields as well as a one-pot version of the reaction. The substrate scope was well studied but the one-pot reaction was not well tested (one substrate).