Influence of steric demand on ruthenium-catalyzed cycloaddition of sterically hindered azides

The RuAAC of sterically hindered 2,2-diaryl-2-azidoamines and terminal alkynes resulted in the unprecedented formation of 1,4-disubstituted-1,2,3-triazoles. A control experiment with 2-(azidomethyl)pyrrolidine revealed the usual selectivity with RuAAC and the reactions of azides with intermediate bulkiness gave mixtures of 1,4- and 1,5-regioisomers. The results suggest that the steric demands could annul the preference and influence on the regioselectivity of RuAAC substantially. Steric effects play a dominant role on the regioselectivity of RuAAC.