Regioselective conversion of alkynes to 4-substituted and 3,4-disubstituted isoxazoles using titanium-catalyzed multicomponent coupling reactions

Conditions have been developed for the regioselective synthesis of 4-substituted isoxazoles from terminal alkynes and 3,4-disubstituted isoxazoles from internal alkynes. The methodology involves a one-pot titanium-catalyzed multicomponent coupling reaction followed by simple hydroxylamine hydrochloride addition.