Ethyl 2-chloroacetoacetate → Ethyl 6-bromo-8-[(2,6-difluorobenzyl)oxy]-2-methylimidazo[1,2-a]pyridine-3-carboxylate

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Reaction Steps

24 g of 5-bromo-3-[(2,6-difluorobenzyl)oxy]pyridine-2-amine (Example 17A; 76.2 mmol; 1 equivalent) were initially charged in 400 ml of ethanol, 16 g of powdered molecular sieve 3 Å and 52.7 ml of ethyl 2-chloroacetoacetate (380.8 mmol; 5 equivalents) were added and the mixture was heated at reflux overnight. A further 8 g of molecular sieve were added, and the mixture was heated at reflux for a further 24 h. The reaction mixture was concentrated and the residue was taken up in dichloromethane and chromatographed on silica gel (dichloromethane/methanol 20:1 as mobile phase). The product-containing fractions were concentrated and the residue was stirred with 100 ml of diethyl ether for 30 min, and the product was filtered off, washed with a little diethyl ether and dried. This gave 15 g (45% of theory) of the title compound.

Provenance & Evidence