Sulfuric Acid → N-(2-methoxy-3,4-methylenedioxybenzyl)-N-(p-toluenesulfonyl)aminoacetaldehyde diethylacetal

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Reaction Conditions

Reaction Steps

5.67 g (20 mmol) of N-(2-methoxy-3,4-methylenedioxybenzyl)-N-methylaminoacetaldehyde dimethylacetal (1) obtained in Example 3 was dissolved in 40 ml of 6N sulfuric acid. After stirring at 76°-7° C. for 1.5 hours, the reaction mixture was cooled and the pH was controlled to about 11 by adding 25% aqueous solution of sodium hydroxide at a temperature lower than 30° C. It was extracted with 35 ml and then 10 ml of methylene chloride successively, which were combined and washed with 20 ml of water and then dried over anhydrous magnesium sulfate. The solvent was concentrated under vacuum, the residue was dissolved under heating by adding 12 ml of ethanol and then cooled to 5° C. to deposit crystals. The crystals were collected by filtration, washed with 3 ml of cold ethanol and then dried under vacuum to obtain 3.71 g (yield 78%) of 4-hydroxy-8-methoxy-2-methyl-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline (2), m.p. 152°-3° C.

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