1,1′-Carbonyldiimidazole (1.17 g, 7.2 mmol) was added to a stirred solution of 2-bromo-3-cyclohexyl-1H-indole-6-carboxylic acid (2.03 g, 6.3 mmol) in THF (6 mL) at 22° C. The evolution of CO2 was instantaneous and when it slowed the solution was heated at 50° C. for 1 hr and then cooled to 22° C. N,N-Dimethylsulfamide (0.94 g, 7.56 mmol) was added followed by the dropwise addition of a solution of DBU (1.34 g, 8.8 mmol) in THF (4 mL). Stirring was continued for 24 hr. The mixture was partitioned between ethyl acetate and dilute HCl. The ethyl acetate layer was washed with water followed by brine and dried over Na2SO4. The extract was concentrated to dryness to leave the titled product as a pale yellow friable froth (2.0 g, 74%) of substantial purity (90%). 1H NMR (300 MHz, DMSO-D6) δ ppm 1.28-1.49 (m, 3 H) 1.59-2.04 (m, 7 H) 2.74-2.82 (m, 1 H) 2.88 (s, 6 H) 7.57 (dd, J=8.42, 1.46 Hz, 1 H) 7.74 (d, J=8.78 Hz, 1 H) 7.91 (s, 1 H) 11.71 (s, 1 H) 12.08 (s, 1 H).
