Triphenylphosphine → rac-Ethyl 8-[1-(2,6-difluorophenyl)ethoxy]-2,6-dimethylimidazo[1,2-a]pyridine-3-carboxylate

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Reaction Steps

5.50 g (23.5 mmol) of ethyl 8-hydroxy-2,6-dimethylimidazo[1,2-a]pyridine-3-carboxylate Example 87A, 4.46 g (28.2 mmol) of 1-(2,6-difluorophenyl)ethanol, 5.35 ml (27.0 mmol) of diisopropyl azodicarboxylate and 7.08 g (27.0 mmol) of triphenylphosphine were dissolved in 141 ml of THF, and the mixture was stirred at RT for 2 h. 0.70 ml (3.5 mmol) of diisopropyl azodicarboxylate and 0.62 g (2.3 mmol) of triphenylphosphine were added to the reaction mixture, and the reaction solution was stirred at RT for 1 h. The precipitated solid was filtered off and dried under high vacuum. This gave 4.6 g (52.8% of theory; purity 100%) of the title compound. The filtrate was concentrated and purified twice by silica gel chromatography (cyclohexane:ethyl acetate gradient=from 8:1 to 4:1). All product-containing fractions were re-purified by preparative HPLC (RP18 column, mobile phase: acetonitrile/water gradient with addition of 0.1% TFA). This gave another 2.16 g (25% of theory) of the target compound.

Provenance & Evidence