Dimethyl Sulfoxide → 6-cyano-2,2-dimethyl-4-(1,2-dihydro-2-oxo-4-formyl-1-pyridinyl)-2H-benzo[b]pyran

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Reaction Steps

In 200 ml of anhydrous methylene chloride, is dissolved 3.84 ml of oxalyl chloride. After cooling the resulting solution to -50° C. to -60° C., 6.24 ml of dimethyl sulfoxide is dropped thereinto and stirred at that temperature for 5 minutes. Then, 200 ml of a solution containing 12.3 g of 6-cyano-2,2-dimethyl-4-(1,2-dihydro-2-oxo-4-hydroxymethyl-1-pyridinyl)-2H-benzo[b]pyran obtained in Example 9 (or Example 22) in anhydrous methylene chloride is added at that temperature over a period of 25 minutes and reacted at that temperature for 20 minutes. After adding 27.9 ml of triethylamine to the reaction mixture and stirred at that temperature for 10 minutes, the temperature is slowly elevated to room temperature. After stirring the mixture at room temperature for an additional one hour, the reaction is stopped by adding water, and the reaction mixture is extracted with methylene chloride. The organic layer is washed with saturated aqueous solution of sodium chloride and dried over anhydrous sodium sulfate. The inorganic matter is filtered off and the filtrate is concentrated under reduced pressure. The residue is purified by silica gel column chromatography using 1/30 mixture of methanol/methylene chloride as a developing solvent. Thus, 12.2 g of 6-cyano-2,2-dimethyl-4-(1,2-dihydro-2-oxo-4-formyl-1-pyridinyl)-2H-benzo[b]pyran is obtained.

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