[Synthesis]
Preparation of Example 20: A suspension of 1-benzyl-spiro[benzofuran-3,4-piperidine] (1.0 g, 3.58 mmol) was formed with 10% palladium carbon (750 mg) in ethanol (30 mL). To this suspension was added spiro H-benzofuran-3,4'-piperidine ammonium formate (1.13 g, 17.94 mmol) in one go. The reaction mixture was heated to reflux for 1.25 hours. After completion of the reaction, the mixture was cooled, filtered through Arbocel and the filter cake was washed with additional ethanol. The filtrate was evaporated under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography using a gradient elution of dichloromethane: methanol: 0.88 ammonia (100:0:0 to 90:10:1) to give 2H-spiro[benzofuran-3,4'-piperidinium] as a cream-colored solid (489 mg, 72% yield). The product was confirmed by 1HNMR (CDCl3, 400MHz): δ 1.72 (m, 2H), 1.80-1.96 (m, 2H), 2.70 (m, 2H), 3.11 (m, 2H), 4.40 (s, 2H), 6.79 (m, 1H), 6.88 (m, 1H), 7.13 (m, 1H), 7.14 (m, 1H). LRMS (ES+): m/z 190 [MH]+. |