A solution of lithium diisopropylamide (0.50 M, 72.6 mL, 36.2 mmol, 1.6 equiv) was added via cannula to a solution of 1-tert-butyl 6-methyl 1H-indole-1,6-dicarboxylate (1-5, 6.23 g, 22.6 mmol) in THF (100 mL) at −78° C. The resulting mixture was stirred for 2 hours at −78° C. before a solution of trimethyltin chloride in THF (2.3 M, 19.7 ml, 45.3 mmol, 2.00 equiv) was added. The resulting solution was warmed to 0° C. for 15 minutes, then partitioned between EtOAc (2×150 mL) and aqueous half-saturated NH4Cl solution (200 mL). The combined organics layers were dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (100% hexanes initially, grading to 20% EtOAc in hexanes) to afford 1-tert-butyl 6-methyl 2-(trimethylstannyl)-1H-indole-1,6-dicarboxylate (1-6) as an orange oil. 1H NMR (300 MHz, CDCl3) δ 8.74 (s, 1H), 7.88 (dd, 1H, J=8.2, 1.8 Hz), 7.53 (d, 1H, J=8.2 Hz), 6.77 (br s, 1H), 3.95 (s, 3H), 1.74 (s, 9H), 0.33 (s, 9H).
