Table 1.

Optimization results for the cross-coupling of 2-chloropyridine (1a) with ethyl 4-bromobutyrate (2a).^a

Entry	Change from above conditions	Yield (%)b
1	None	82
2	10 mol% NiBr2•3H2O/4	74c
3	1 equiv each 1a and 2a	78
4	1.1 equiv 1a	71
5	1,10-phenanthroline (5) in place of 4	64
6	4,4′-di-t-butyl-2,2′-bipyridine (6) in place of 4	66
7	4,4′-di-methoxy-butyl-2,2′-bipyridine (7) in place of 4	69
8	4,4′,4″-tri-tert-butyl-2,2′,:6′,2″-terpyridine (8) in place of 4	15
9	NiCl2(glyme) in place of NiBr2•3H2O	79
10	Reaction run at 20 °C	55c
11	Reaction run at 60 °C	70c
12	Reaction run at 80 °C	62c
13	25% DMA in THF in place of DMF	15d
14	Zn0 (<10 μm) in place of Mn0	19e
15	Al0/PbBr2 in place of Mn0	2e,g

^aReaction conditions: DMF (1 mL), NiBr₂•3H₂O (0.15 mmol), 1a (3.00 mmol), 2a (3.30 mmol), ligand (0.15 mmol), and Mn⁰ (6.00 mmol) were added to a 1 dram vial on the bench top and heated under air for 4–22 h.

^bGC yield corrected vs. dodecane internal standard.

^cIsolated yield.

^dObserved partial conversion of starting material at 24 h.

^eMajor coupled product was the alkyl dimer.

^fNo reaction of 2a was observed.