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

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Reaction Steps

The above solution from Example 20A is admixed with 61.25 ml (60.77 g, 0.613 mol) of dimethylaminoacrolein and 56.28 ml (83.88 g, 0.736 mol) of trifluoroacetic acid, and the mixture is boiled under argon for 3 days. The solvent is subsequently evaporated under reduced pressure and the residue is added to 2 l of water, and the mixture is extracted three times with 1 l of ethyl acetate in each case. The combined organic phases are dried with magnesium sulphate and concentrated using a rotary evaporator. The mixture is chromatographed over 2.5 kg of silica gel and eluted using a toluene/toluene-ethyl acetate=4:1 gradient.

Provenance & Evidence