Steric character is one of the most fundamental factors to determine the reactivity of the substrate in organic synthesis. In bimolecular reaction, the sterically-bulky group situated close to the reactive center generally prevents the approach of the reaction partner retarding the bond formation. This report describes, to the contrary, significantly enhanced reactivity of 2,6-disubstituted phenyl azides observed in catalyst-free 1,3-dipolar cycloaddition with alkynes, unexpectedly reacting faster than unsubstituted phenyl azide and even more faster than unhindered alkyl azide, despite the steric hindrance adjacent to the reactive azido group. Experimental and computational studies have indicated that the steric hindrance eliciting the inhibition of resonance between azido group and the aromatic ring is the primary cause of this apparently-paradoxical phenomenon. This is the first type of steric acceleration, indicating a possibility of designing a highly reactive functional group by strategically locating it in the sterically-congested environment.

A facile strategy for the synthesis of trifunctional molecules involving three sequential selective triazole-forming reactions is proposed. This method exploits three kinds of mechanistically different azido-type-selective cycloadditions. Three different azidophiles could be efficiently connected to a triazido platform molecule with three types of azido groups in a consecutive manner, which rendered a practical trifunctional molecule readily available.