To a mixture of 755 mg (2.34 mmole) of 8-chloro-11-(1-methyl-4-piperidylidene)-11H-benzo[5,6]cyclohepta[1,2-b]pyridine and 1.5 mL of triethylamine in 25 mL of dry toluene at room temperature and under a nitrogen atmosphere was added 650 μL (4.72 mmole) of 2,2,2-trichloroethyl chloroformate. The mixture was then heated to 90° C. Additional amounts of the chloroformate (500 μL and 300 μL) and triethylamine (1.0 mL each time) were added to the mixture after 2 hr. and 3 hr. 40 min., respectively. After a total reaction time of 5 hr. the mixture was poured into water and extracted three times with CH2Cl2. The combined organic portions were dried over MgSO4, filtered and concentrated in vacuo. The residue was purified via flash chromatography [11/2% MeOH in CH2Cl2 ] to afford 639 mg (56%) of the title compound as a glass.
