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

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Reaction Conditions

Reaction Steps

62.29 g (0.2 mol) of N-(2-methoxy-3,4-methylenedioxybenzyl)-N-methylaminoacetaldehyde dimethylacetal (1) obtained in Example 2 was dissolved in 400 ml of 6N sulfuric acid. After stirring at 76°-78° C. for 1.5 hours, the reaction mixture was cooled and pH was adjusted to about 11 by adding 25% aqueous solution of sodium hydroxide at temperature lower than 30° C. It was extracted with 200 ml and then 100 ml of methylene chloride successively, which were combined and washed with 100 ml of water and then dried over anhydrous magnesium sulfate. The salt was filtered out and the filtrate was concentrated under vacuum. The residue was dissolved under heating by adding 120 ml of ethanol and then cooled to 5° C. to deposit crystals. The crystals were collected by filtration, washed with 30 ml of cold ethanol and then dried under vacuum to obtain 38.09 g (yield 83%) of 4-hydroxy-8-methoxy-2-methyl- 6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline (2), m.p. 152°-3° C. IR and NMR spectra of the resultant product are listed below. ##STR35##

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