Trifluoroacetic acid → 1-Benzyl-4-(4-chloro-phenyl)-2,5-dihydro-1H-pyrrole-3-carboxylic acid

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Reaction Conditions

Reaction Steps

At r.t., a solution of N-(methoxymethyl)-N-(phenylmethyl)-N-(trimethylsilyl)methyl amine (116.8 g, 0.49 mol) in CH2Cl2 (260 ml) was added dropwise over 90 min to a stirred solution of (4-chloro-phenyl)-propynoic acid ethyl ester (72.0 g, 0.34 mol) and trifluoroacetic acid (2.5 ml, 0.03 mol) in CH2Cl2 (350 ml). The reaction mixture was stirred at 25° C. overnight and afterwards evaporated to dryness. The residue was dissolved in dioxane (0.8 l); an aqueous solution of NaOH (91.0 ml, 1.02 mol, 3 eq.) was added, and the resulting emulsion was stirred at r.t. for 48 h. The low boiling organic solvent was removed under vacuum, water (0.9 l) was added, and the aqueous layer was separated and washed with TBME (1 l). The aqueous layer was then acidified to a pH value of 2.5 by addition of 25% HCl. The resulting suspension was stirred overnight; the white precipitate was filtered off, washed with water and ethanol and dried under high vacuum to yield 62.0 g (60%) of IIa as a white solid.

Provenance & Evidence