Trifluoroacetic acid → 3-Ethoxycarbonyl-1-(2-fluorbenzyl)-1H-pyrazolo-(3,4,5)-pyridin

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Reaction Steps

The solution obtained from 2A) is mixed with 61.25 ml (60.77 g, 0.613 mmol) of dimethylaminoacrolein and 56.28 ml (83.88 g, 0.736 mol) of trifluoroacetic acid and boiled under argon for 3 days. The solvent is then evaporated in vacuo, and the residue is added to 2 l of water and extracted three times with 1 l of ethyl acetate each time. The combined organic phases are dried over magnesium sulfate and concentrated in a rotary evaporator. Chromatography is carried out on 2.5 kg of silica gel, eluting with a toluene/toluene-ethyl acetate=4:1 gradient. Yield: 91.6 g (49.9% of theory over two stages).

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