A mixture of ethyl carbamate (0.237 g, 2.67 mmol) and KOtBu (0.259 g, 2.310 mmol) in NMP (8.89 mL) was heated at 100° C. for 15 min. 1-(((3S,5S)-5-methyl-1-oxaspiro[2.5]octan-5-ylmethyl)-1H-benzo[d]imidazole-6-carbonitrile (0.500 g, 1.777 mmol) was then added. The reaction mixture was stirred overnight (stopped heating at some point because of storm power outage). The reaction mixture was heated at 100° C. and stirred for an additional 6 h. Additional ethyl carbamate (0.237 g, 2.67 mmol) and KOtBu (0.065 g, 0.578 mmol) were added and stirred for 16 h. Additional ethyl carbamate (0.237 g, 2.67 mmol) and KOtBu (0.130 g, 1.156 mmol) were then added and heated at 110° C. for 16 h. The reaction mixture was heated at 130° C. for 2 days. Additional ethyl carbamate (0.237 g, 2.67 mmol) and KOtBu (0.065 g, 0.578 mmol) were added and mixture stirred for additional 3 h. The reaction mixture was heated at 110° C. for an additional 3 days, followed by the addition of 2N NaOH (30 mL) and EtOAc (75 mL). The layers were then separated and the organic layer washed with water (3×50 mL). The organic layer was dried over Na2SO4, filtered, and concentrated. The compound was loaded onto florisil and purified using silica gel chromatography CISCO): 1-3.5% MeOH/DCM (18 min), 3.5% (7 min), 25 g silica. Product eluted at 13 min. The product was dried under high vacuum at 40° C. overnight. 1-{[(5S,7S)-7-methyl-2-oxo-1-oxa-3-azaspiro[4.5]dec-7-yl]methyl}-1H-benzimidazole-6-carbonitrile was obtained as a white solid (336 mg, 55.4% yield). MS (m/z) 325 (M+H+).
