Preferential cross‐coupling of naphthol derivatives mediated by copper(II)

Preferential cross‐coupling of differently N ‐substituted amides of 3‐hydroxy‐2‐naphthoic acids 1 and 2 catalyzed by Cu(OH)Cl•TMEDA was observed. The reaction mechanism was investigated using mass spectrometry tools. It was shown that the complexation properties of the N ‐substituent significantly influence the properties of the corresponding copper complexes of the deprotonated compounds ([(1‐H)Cu(TMEDA)] + and [(2‐H)Cu(TMEDA)] + ). Analysis of the fragmentation patterns of the copper complexes revealed that while the former is prone to the one electron oxidation of (1‐H)ˉ, the latter has a larger binding energy between (2‐H)ˉ and copper(II). Interplay between the abundance of the copper complexes and their reactivities explains the preferential cross‐coupling . The results are further supported by exploratory density functional theory calculations. Copyright © 2013 John Wiley & Sons, Ltd.