A solution of methyl 11-cyclohexyl-6-hydroxy-8-methoxy-6H-isoindolo[2,1-a]indole-3-carboxylate (2.9 g, 7.4 mmol), methyl 2-(dimethoxyphosphoryl)acrylate (2.6 g, 11 mmol), cesium carbonate (3.6 g, 11 mmol) in DMF (20 mL) was heated at 60° C. for 2 h and cooled to rt. The stirring reaction mixture was diluted with H2O (50 mL) and the precipitates were collected by filtration to yield dimethyl 13-cyclohexyl-3-methoxy-7H-indolo[2,1-a][2]benzazepine-6,10-dicarboxylate (3.3 g, 7.1 mmol, 97%) as a yellow solid which was used without further purification. LCMS: m/e 460 (M+H)+, ret time 3.35 min, column B, 3 minute gradient.
