[CH2:1]([O:3][C:4]([C:6]1[O:7][C:8]2[CH:15]=[CH:14][CH:13]=[C:12]([C:16]#[CH:17])[C:9]=2[C:10]=1[CH3:11])=[O:5])[CH3:2].C(OC(OC(C)(C)C)=O)(OC(C)(C)C)=O.[N+:33]([CH2:36][CH3:37])([O-])=[O:34]>C(#N)C.CN(C)C1C=CN=CC=1>[CH2:1]([O:3][C:4]([C:6]1[O:7][C:8]2[CH:15]=[CH:14][CH:13]=[C:12]([C:16]3[O:34][N:33]=[C:36]([CH3:37])[CH:17]=3)[C:9]=2[C:10]=1[CH3:11])=[O:5])[CH3:2]
To a solution of 4-ethynyl-3-methyl-benzofuran-2-carboxylic acid ethyl ester (228 mg, 0.99 mmol, 1 eq.) in acetonitrile (5 mL) under argon, was added di-tert-butyl dicarbonate (327 mg, 1.5 mmol, 1.5 eq.), and 4-(dimethylamino)pyridine (12 mg, 0.1 mmol, 0.1 eq.). Nitroethane (79 uL, 1.1 mmol, and 1.1 eq.) in acetonitrile (5 mL) was added drop-wise to the reaction mixture, and the reaction was stirred at room temperature for 72 hours. After work-up and flash column chromatography, 3-methyl-4-(3-methyl-isoxazol-5-yl)-benzofuran-2-carboxylic acid ethyl ester was obtained in 25% yield. 1H NMR (400 MHz, DMSO-d6) δ ppm 1.4 (t, J=7.1 Hz, 3 H) 2.3 (s, 3 H) 2.4 (s, 3 H) 4.4 (q, J=7.1 Hz, 2 H) 6.8 (s, 1 H) 7.5 (dd, J=7.5, 0.9 Hz, 1 H) 7.6 (m, 1 H) 7.9 (dd, J=8.5, 0.9 Hz, 1 H).
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