[CH:1]([NH2:3])=O.[NH2:4][C:5]1[S:6][C:7]2[CH2:22][C:17]3([O:21][CH2:20][CH2:19][O:18]3)[CH2:16][CH2:15][C:8]=2[C:9]=1[C:10](OCC)=[O:11].C([O-])=O.[NH4+]>>[O:18]1[CH2:19][CH2:20][O:21][C:17]21[CH2:16][CH2:15][C:8]1[C:9]3[C:10](=[O:11])[NH:3][CH:1]=[N:4][C:5]=3[S:6][C:7]=1[CH2:22]2To a stirring 225 mL formamide solution of ethyl 2-amino-4,7-dihydro-5H-spiro[1-benzothiophene-6,2′-[1,3]dioxolane]-3-carboxylate (40.0 g, 0.142 mol) was added ammonium formate (17.8 g, 0.282 mol). The contents were stirred with heating at 140° C. for 16 h, after which time the heterogeneous contents were removed from heating, and allowed to cool to rt. The contents were filtered, the solid filter cake washed with water (2×60 mL), and suction dried overnight to afford the desired product as an off-white solid (33.0 g, 88%). 1H-NMR (DMSO-d6) δ 12.35 (broad s, 1H), 8.00 (s, 1H), 3.92 (s, 4H), 2.95 (t, 2H), 2.91 (s, 2H), 1.83 (t, 2H); LCMS RT=1.87 min; [M+H]+=265.2.
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