[CH3:1][O:2][C:3]1[CH:7]=[CH:6][S:5][C:4]=1C(O)=O.C([N:13]([CH2:16]C)CC)C.[NH2:18][C:19]1[CH:24]=[CH:23][C:22]([N+:25]([O-:27])=[O:26])=[CH:21][C:20]=1[OH:28].P(N=[N+]=[N-])(OC1C=CC=CC=1)(OC1C=CC=CC=1)=[O:30]>C1(C)C=CC=CC=1>[OH:28][C:20]1[CH:21]=[C:22]([N+:25]([O-:27])=[O:26])[CH:23]=[CH:24][C:19]=1[NH:18][C:16]([NH:13][C:4]1[S:5][CH:6]=[CH:7][C:3]=1[O:2][CH3:1])=[O:30]
To a solution of 3-methoxy-2-thiophene carboxylic acid (example 11a, 200 mg, 1.27 mmol) in toluene, (PhO)2PON3 (0.33 mL) and triethylamine (1. 1 equiv., 0.25 mL) were added. The reaction mixture was stirred at 70° C. for 2 hours and cooled down to room temperature then 2-amino-5-nitrophenol was added. The reaction mixture was stirred at 70° C. overnight. The reaction mixture was partitioned between 5% citric acid and ethyl acetate. The organic layer was separated and the aqueous layer was extracted three times with ethyl acetate. The organic extracts were combined, dried over MgSO4, filtered and concentrated under reduced pressure. Chromatography of the resulting solid on silica gel (hexane:ethyl acetate; 1:1) gave the product (190 mg, 48%). 1H NMR (CD3OD/CDCl3): d 8.38 (d, 1H, J=5.0 Hz), 7.85 (dd, 1H, J=5.0 Hz and J=1.25 Hz), 7.76 (d, 1H, J=2.5 Hz), 6.9 (s, 2H), 3.95 (s, 3H); El-MS m/z 309 (M+H)+; Anal. (C12H11N3O5S) C, H, N.
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