FC(F)(F)S(O[C:7]1[C:15]2[N:11]([CH:12]=[CH:13][CH:14]=2)[C:10]([C:16]([O:18][CH2:19][CH3:20])=[O:17])=[CH:9][CH:8]=1)(=O)=O.[SiH](CC)(CC)CC.CN([CH:33]=[O:34])C>C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.Cl[Pd]Cl.[Fe+2]>[CH:33]([C:7]1[C:15]2[N:11]([CH:12]=[CH:13][CH:14]=2)[C:10]([C:16]([O:18][CH2:19][CH3:20])=[O:17])=[CH:9][CH:8]=1)=[O:34]To a solution of ethyl 8-(((trifluoromethyl)sulfonyl)oxy)indolizine-5-carboxylate (4 g, 11.87 mmol) in DMF (1200 mL) was added TEA (3.6 g, 35.61 mmol), Et3SiH (4.14 g, 35.61 mmol) and Pd(dppf)2Cl2 (0.9 g, 10 mol %) under N2. The reaction mixture was stirred at 60° C. under CO (50 psi) overnight. The mixture was concentrated and to the residue were added EA and water, washed with brine, dried and concentrated and purified by column to give product ethyl 8-formylindolizine-5-carboxylate (1 g, yield 39%). 1H NMR (400 MHz, DMSO-d6): δ 10.15 (s, 1H), 8.61 (s, 1H), 7.76 (m, 1H), 7.63 (m, 1H), 7.37 (m, 1H), 7.10 (m, 1H), 4.46 (q, 2H), 1.39 (t, 3H) ppm.
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