Dimethyl Sulfoxide → 2-(2-Methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-3-yl)acetaldehyde

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Reaction Steps

To a stirred mixture of 2.2 mL (25.22 mmoles) of oxalyl chloride in 70 mL of anhydrous methylene chloride at low temperature (−70° C. to −50° C.) and under inert atmosphere, 4.1 mL (57.78 mmoles) of dimethyl sulfoxide were added. Then, a solution of 5 g (24.02 mmoles) of 3-(2-hydroxyethyl)-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one (X) in 30 mL of methylene chloride was added. After 30 minutes, 14.6 mL (104.75 mmoles) of triethylamine were added and the mixture was warmed for 45 minutes at room temperature. 75 mL of water were poured and the organic phase was decanted. The aqueous phase was removed with methylene chloride. All the organic phases were dried over anhydrous sodium sulphate, filtered and the solvent was evaporated to give 4.90 g (99%) of (2-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-3-yl)-acetaldehyde (II) as an oily residue. The compound thus obtained was pure enough as to be used in the subsequent reaction step with no prior purification.

Provenance & Evidence