n-Bu₄NI/K₂S₂O₈-MEDIATED C-N COUPLING BETWEEN ALDEHYDES AND AMIDES

n-Bu₄NI/K₂S₂O₈ mediated C-N coupling between aldehydes and amides is reported. A strong electronic effect is observed on the aromatic aldehyde substrates. The transformylation from aldehyde to amide takes place exclusively when an aromatic aldehyde bears electron-donating groups at either the ortho or para position of the formyl group, while the cross-dehydrogenative coupling dominates in the absence of these groups. Both the density functional theory (DFT) thermochemistry calculations and experimental data support the proposed single electron transfer mechanism with the formation of an acyl radical intermediate in the cross-dehydrogenative coupling. The n-Bu₄NI/K₂S₂O₈ mediated oxidative cyclization between 2-aminobenzamide and aldehydes is also reported, with four quinazolin-4(3H)-ones prepared in 65-99% yields.