On the origin of copper(i) catalysts from copper(ii) precursors in C–N and C–O cross-couplings

Cu(II) precursors ligated to phenanthrolines are reduced in situ by alcohols or amines in the presence of a base (Cs(2)CO(3)) to generate Cu(I) species which are active catalysts in C-N and C-O cross-coupling reactions. The conversion Cu(II) --> Cu(I) has been evidenced and monitored by UV-vis and NMR spectroscopy.