At r.t., a solution of N-(methoxymethyl)-N-(phenylmethyl)-N-(trimethylsilyl)methyl amine (262.5 g, 1.06 mol) in CH2Cl2 (0.6 l) was added dropwise over 60 min to a solution of (3,4-dichloro-phenyl)-propynoic acid ethyl ester (172.0 g, 0.71 mol) and trifluoroacetic acid (5.4 ml, 0.07 mol) in CH2Cl2 (0.7 l). The reaction mixture was stirred at 25° C. for 2 h. The reaction mixture was then evaporated to dryness, and the residue was dissolved in dioxane (1.6 l). An aqueous solution of NaOH (1.0 l, 1.9 mol, 2.8 eq.) was added. The resulting emulsion was stirred at r.t. for 20 h, and the low boiling organic solvent was removed under vacuum. Water (2.0 l) was added, and the aqueous layer was separated and washed with TBME (2 times 1.2 l). The aqueous layer was then acidified to a pH value of 2.5 by addition of 25% HCl. The resulting suspension was then stirred overnight, and the white precipitate was filtered off, washed with water and ethanol and dried under high vacuum to yield 205.0 g (83%) of IIb as a white solid.
