ClC1C=CC=C(C(OO)=O)C=1.[CH3:12][O:13][C:14](=[O:28])[C:15]1[CH:20]=[CH:19][C:18]([C:21]#[C:22][CH2:23][N:24]([CH3:26])[CH3:25])=[CH:17][C:16]=1[Cl:27].C(OCC)C>ClCCl>[CH3:12][O:13][C:14](=[O:28])[C:15]1[CH:20]=[CH:19][C:18]([CH2:21][CH:22]=[CH:23][N:24]([CH3:25])[CH3:26])=[CH:17][C:16]=1[Cl:27]Under an atmosphere of nitrogen, purified meta-chloroperbenzoic acid (16.0 g, 93 mmol) was added portionwise to a stirred solution of 2-chloro-4-(3-dimethylaminopropyn-1-yl)-benzoic acid methyl ester of Step A (23.5 g, 93.4 mmol) in 200 mL of dichloromethane at −10° C. After the addition was complete, the solution was stirred at reduced temperature for 30 minutes and then filtered through a column of basic alumina (400 g, Brockman activity I) packed with dichloromethanemethanol (9:1, v/v). The intermediate N-oxide was eluted with the above solvent system. The dichloromethane was then carefully replaced with methanol by evaporation at or below room temperature, taking care that the mixture is never allowed to evaporate to dryness. The methanolic solution was heated at 60° C. overnight, and then was concentrated in vacuo. The residue was purified by flash chromatography (on Merck-60 silica gel, hexane-ethyl acetate 1:1) to give 12.1 g of a slightly impure product. Trituration with diethyl ether provided the pure title compound (6.15 g) as an orange solid.
Loading…
