5-Methylene-hexahydro-cyclopenta[c]pyrrole-2-carboxylic acid dimethylamide 11a (1.6 g, 8.23 mmol) was dissolved in 30 mL of dichloromethane with stirring followed by addition of trimethylsilyl cyanide (4.08 g, 41.2 mmol) and silver perchlorate (5.12 g, 24.7 mmol) under nitrogen atmosphere. The reaction mixture was stirred overnight at room temperature and then some of the reaction mixture was treated with saturated aqueous sodium carbonate. The reaction was monitored by TLC, which showed that there remained most of the starting materials. Then the mixture was treated with 20 mL of saturated aqueous sodium carbonate upon cooling by an ice-water bath, and the reaction released heat. After 10 minutes, the mixture was filtered to remove the residue. The separated aqueous phase was extracted with ethyl acetate (50 mL×4). The combined organic extracts were dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain 5-isocyano-5-methyl-hexahydro-cyclopenta[c]pyrrole-2-carboxylic acid dimethylamide 11b (0.33 g, yield 18.1%) as a light yellow oil.
