p-Toluenesulfonic acid → (E)-5,6,9,10-Tetrahydro-10-[(5-methyl-1H-imidazol-4-yl)methylene]-4H-pyrido[3,2,1-jk]carbazol-11(8H)-one

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Reaction Steps

n-Butyllithium (1.73M in hexane; 4.14 ml) was added dropwise to a cold (-70°) stirred solution of diisopropylamine (1 ml) in dry THF (10 ml) under nitrogen. The resulting solution was stirred at 0° for 30 min, cooled to -70° and added dropwise to a cold (-70°) stirred suspension of 5,6,9,10-tetrahydro-4H-pyrido[3,2,1-jk]carbazol-11(8H)-one (645 mg) in dry THF (20 ml) under nitrogen. The solution was allowed to reach 0° over 1 h, cooled to -70° and a solution of 5-methyl-1-(triphenylmethyl)-1H-imidazole-4-carboxaldehyde (1.01 g) in dry THF (10 ml) was added dropwise. The stirred mixture was allowed to reach room temperature over 2 h, and then stirred for a further 3 h. The solution was cooled to -70° and treated with acetic acid (8 ml) and p-toluenesulphonic acid (5.44 g) and heated at reflux for 16 h. The solvent was removed in vacuo, the residue was treated with 8% sodium bicarbonate solution (150 ml) and extracted with dichloromethane (4×50 ml). The combined, dried organic extracts were evaporated to give a gum (ca. 2 g) which was purified by FCC eluting with System A to give the title compound (145 mg) as a solid, m.p. 260°-264°.

Provenance & Evidence