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

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Reaction Steps

The solution obtained from 3A) is treated 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 boiled under argon for 3 days. The solvent is then evaporated in vacuo, the residue is added to 2 l of water and the mixture is extracted three times with 1 l of ethyl acetate each time. The combined organic phases are dried using magnesium sulphate and concentrated in a rotary evaporator. The residue is chromatographed on 2.5 g of silica gel and eluted with a toluene/toluene-ethyl acetate=4:1 gradient. Yield: 91.6 g (49.9% of theory over two steps).

Provenance & Evidence