Table 3.

Substrate scope for the deaminative coupling of pyridinium salts with carboxylic acid derivatives.

^[a]After initial acid fluoride formation using carboxylic acid (0.5 mmol, 1 equiv), TFFH (0.5 mmol, 1 equiv) and proton sponge (0.5 mmol, 1 equiv), the coupling was run on 0.5 mmol scale with a 1:1 ratio of starting materials, ligand L5 (0.05 mmol, 10 mol%), Mn (0.75 mmol, 1.5 equiv) in NMP (3 mL) at 60 °C for 24 h.

^[b]Reaction run at 0.5 mmol scale using pyridinium salt (0.75 mmol, 1.5 equiv) and pre-formed 2-pyridyl ester (0.5 mmol, 1 equiv) with NiBr₂(dme) (0.05 mmol, 10 mol%), ligand L4 (0.05 mmol, 10 mol%), Mn (0.75 mmol, 1.5 equiv) in THF at r.t. for 24 h.

^[c]Reaction run on 5 mmol scale on benchtop, see Supporting Information.

^[d]Pre-formed acyl fluoride was used.

^[e]L2 used instead of L5.

^[f]L1 was used instead of L5.

^[g]Reaction run on 0.178 mmol scale at standard concentration.

^[h]NMR yield shown. Product was not separated from impurities, see Supporting Information for details.

Boc = tert-butoxycarbonyl, TBS = tert-butyldimethylsilyl.