A mixture of 0.1 g (0.5 mM) of 1-ethyl-2-methylbenzimidazole-5-yl methyl ketone and 0.1 g (0.5 mM) 4-formyl-N-benzylpiperidine in 10 mL of tetrahydrofuran (THF) was cooled to -78° C. under a nitrogen atmosphere. To this mixture were added dropwise 0.5 mL (0.5 mM) of a 1 M solution of lithium bis(trimethylsilyl)amide in THF. The reaction was stirred at -78° C. for 1 hour, then warmed to room temperature. To the reaction was added 10 mL of water and the pH was adjusted to 2.0 with 1 N hydrochloric acid (HCl). The mixture was extracted with 15 mL of ethyl acetate. The pH of the water layer was then sequentially adjusted to 3.0, 4.0, 5.0, 6.5, and 8.5 with 1 N NaOH, each time extracting with 15 mL of ethyl acetate. The ethyl acetate extracts at pH=5.0 and 6.5 were combined, dried with sodium sulfate (Na2SO4) and evaporated to yield 50 mg (26%) of the title compound as an oil.
