Iodoethane → 4-Ethoxy-isophthalic acid di-methyl ester

Beteiligte Stoffe

Reaktionsschritte

Into a flask was placed 4-hydroxy-isophthalic acid (25.46 g) and 200 mL of methanol. Concentrated sulfuric acid (20 mL) was slowly added. The mixture was refluxed for 48 hours; upon cooling a copious white precipitate formed, which was collected by filtration. The white solid obtained was washed with water, then dried under vacuum at 50° C. to yield 26.65 g of 4-hydroxy-isophthalic acid dimethyl ester. Iodoethane (3.8 mL, 47.5 mmol) was combined with the ester (5.0 g, 23.8 mmol), powdered cesium carbonate (3.3 g, 23.9 mmol) and anhydrous N,N′-dimethylformamide (40 mL). The mixture was stirred at room temperature overnight. The mixture was concentrated to give a white solid, which was partitioned between ethyl acetate (100 mL) and water (100 mL). The organic phase was further washed with 20 mL of brine, then dried with magnesium sulfate. Concentration yielded a clear oil, which was crystallized by the addition of a small amount of hexanes. The white crystals were collected by filtration and dried under vacuum to yield 5.17 g of 4-ethoxy-isophthalic acid di-methyl ester. This ester (5.10 g, 21.4 mmol) was placed in a mixture of 50% w/w sodium hydroxide (8.73 g) and 50 mL of water. Enough dioxane, about 10 mL, was added to solubilize the solid. The mixture was refluxed until all starting material had been consumed, about 1 hour. The solution was cooled, then acidified with concentrated hydrochloric acid until the pH of the solution was 1. The white precipitate obtained was collected by filtration, rinsed with water, then dried under vacuum overnight to yield 4.49 g of 4-ethoxy-isophthalic acid. This acid (2.0 g, 9.5 mmol) was refluxed in 10 mL of neat thionyl chloride for 3 hours. The excess thionyl chloride was evaporated at reduced pressure to give a white solid, which was dissolved in anhydrous tetrahydrofuran (“THF”), and evaporated at reduced pressure. Half of the resulting material was combined with 3-methoxy-benzylamine (1.22 mL, 9.5 mmol) triethylamine (2.0 mL, 14.3 mmol) and anhydrous THF (20 mL). The mixture was stirred until all the starting material was consumed, about 3 hours. The THF was evaporated at reduced pressure, and the white residue was dissolved in ethyl acetate (100 mL). The organic phase was washed with water (20 mL), 0.1N hydrochloric acid (20 mL), water (20 mL), and brine (20 mL). The organic phase was dried with magnesium sulfate and concentrated to give a white solid. The solid was recrystallized from hot ethyl acetate and collected by filtration. The solid was dried under vacuum at 40° C. to yield 1.56 g of the title compound. MS: M+1=449.2. Microanalysis (C26H28N2O5): Calc'd: C=69.63, H=6.29, N=6.25. Found: C=69.60, H=6.30, N=6.16.

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