[CH2:1]1[CH2:6][CH2:5][C:4]([CH2:11][NH2:12])([CH2:7][C:8]([OH:10])=[O:9])[CH2:3][CH2:2]1.[CH2:13](O)[CH:14]=[CH2:15].S(Cl)([Cl:19])=O>C(OCC)C>[ClH:19].[NH2:12][CH2:11][C:4]1([CH2:7][C:8]([O:10][CH2:15][CH:14]=[CH2:13])=[O:9])[CH2:3][CH2:2][CH2:1][CH2:6][CH2:5]1A dry 500 mL, three-neck, round-bottomed flask was fitted with a magnetic stirring bar and a 100 mL pressure-equalizing addition funnel and flushed with nitrogen gas. The flask was charged with gabapentin (17.1 g, 0.1 mol) and allyl alcohol (100 mL, 1.46 mol) and the entire mixture was cooled to 0° C. in an ice-water bath. Thionyl chloride (22.5 mL, 36 g, 0.3 mol) was added drop-wise over a period of 30 min to the stirred solution, and the reaction mixture allowed to stir for 16 h at room temperature. The mixture was then diluted with diethyl ether (200 mL) and cooled to 0° C. while stirring. After several minutes white crystals formed, and were collected by filtration. The crude compound was recrystallized from a mixture of ethanol and diethyl ether (50 mL: 150 mL) to give the product (13) as a white solid (22 g, 88% yield), m.p: 138-142° C. 1H NMR (CD3OD, 400 MHz): δ 1.36-1.54 (m, 10H), 2.57 (s, 2H), 3.05 (s, 2H), 4.61 (d, 2H), 5.22 (dd, 1H), 5.33 (dd, 1H), 5.90-6.00 (m, 1H). MS (ESI) m/z 212.0 (M+H+).
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