Ligand-controlled phosphine-free Co(II)-catalysed cross-coupling of secondary and primary alcohols

Cobalt(II) complexes (5 mol% Co) bearing phosphine-free N^˄N^˄N pincer ligands efficiently catalyze C–C coupling of secondary and primary alcohols to selectively form α-alkylated ketones with a good functional group compatibility using NaOH (20 mol%) as a base at 120 °C. The NH group on the N^˄N^˄N–Co(II) precatalyst controls the activity and selectivity. This simple catalytic system is involved in the synthesis of quinolones via the dehydrogenative annulation of 2-aminobenzyl alcohols with secondary alcohols.