Mechanistic Aspects of the CuAAC

RuAAC are only in their infancy [108-110]. It is not discussed further here since the focus of this book is on non-precious metals. 

For the conversion of azides and terminal alkynes to 1,4-triazoles, Cu(I) remains the only active species identified so far. Surveys in our laboratories of complexes of all of the first-row transition elements and such ions as Ag(I), Pd(0/II), Pt(II), Au(I/III), and Hg(II), among others, have all failed to produce triazoles, although interesting and complex reactivity has occasionally been seen. We attribute the unique AAC-catalyzing function of Cu(I) to the fortuitous combination of an 

WEAK-DONOR CONDITIONS STRONG-DONOR CONDITIONS 

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