Abstract
Preferential cross-coupling of differently N-substituted amides of 3-hydroxy-2-naphthoic acids 1 and 2 catalyzed by Cu(OH)Cl center dot 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)(-), the latter has a larger binding energy between (2-H)(-) 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.