[CH2:1]([Mg]Br)[CH3:2].C(Br)C.[Mg].[C:9]([O:13][C:14](=[O:23])[C:15]1[CH:20]=[C:19]([CH3:21])[N:18]=[C:17](Cl)[CH:16]=1)([CH3:12])([CH3:11])[CH3:10]>CCOCC.C1COCC1.CN1C(=O)CCC1>[C:9]([O:13][C:14](=[O:23])[C:15]1[CH:20]=[C:19]([CH3:21])[N:18]=[C:17]([CH2:1][CH3:2])[CH:16]=1)([CH3:12])([CH3:11])[CH3:10]A solution of ethylmagnesiumbromide (freshly prepared from ethylbromide (392 mg, 3.6 mmol) and magnesium (83 mg, 3.4 mmol)) in Et2O (10 mL) is added to a cooled (−40° C.) and mechanically stirred solution of 2-chloro-6-methyl-isonicotinic acid tert-butyl ester (0.76 g, 3.34 mmol), Fe(acac)3 (21.2 mg, 0.06 mmol) and NMP (0.6 mL) in THF (60 mL). The mixture is warmed to rt during 0.5 h, diluted with Et2O (150 mL) and quenched with aq. KHSO4 (1 M, 40 mL). The phases are separated and the aq. phase is extracted with Et2O (2×50 mL). The combined organic extracts are dried (MgSO4), filtered and evaporated. The residue is purified by reversed phase MPLC to give 2-ethyl-6-methyl-isonicotinic acid tert-butyl ester; LC-MS: tR=0.67 min, [M+1]+=222.19; 1H NMR (CDCl3): δ 7.44 (s, 2H), 2.83 (q, J=7.6 Hz, 2H), 2.58 (s, 3H), 1.59 (s, 9H), 1.30 (t, J=7.6 Hz, 3H).
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