Yield:-

Reaction Conditions:

Stage #1:2-fluoro-5-chloropyridine with lithium diisopropyl amide at -78; for 7 h;
Stage #2: with iodine for 2 h;

Steps:

4.A
Step A 5-Chloro-2-fluoro-4-iodopyridine (4-2); 5-Chloro-2-fluoropyridine (4-1, 1Og, 76.0 mmol) was adde dropwise at -78 ⁰C to the solution of LDA (2.1M, 400 mL). The reaction mixture was stirred at the same temperature for 7 h, treated with solid I₂, (19.3 g, 76.0 mmol) stirred for 2 h, quenched with water, and partitioned between hexanes and water. The organic layer was washed with IN-HCl and then with brine, separated, dried (MgSO₄) and concentrated in vacuo to give the crude product. Chromatography (SiO₂, hexanes only) afforded the desired isomer (4-2) as a minor product.

References:

MERCK & CO., INC. WO2007/16358, 2007, A1 Location in patent:Page/Page column 38