Benzyl chloroformate → 2,3(1H)-Isoquinolinedicarboxylic acid, 3,4-dihydro-, 2-(phenylMethyl) ester

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Reaction Steps

188 g (1.05 moles) of 3-carboxy-1,2,3,4-tetrahydroisoquinoline are added to 1,050 ml of 1N NaOH at 0°, and 160 ml of benzyl chlorocarbonate and a further 1,050 ml of 1N NaOH are then simultaneously added dropwise at this temperature, while stirring. The mixture is then stirred for 2 hours at room temperature and extracted three times with ether, and the alkaline/aqueous phase is acidified to pH 1 with concentrated HCl. The oil which separates out is extracted with ethyl acetate. The ethyl acetate solution is washed with water until the water phase has a pH of 3.0. After the ethyl acetate solution has been dried over sodium sulfate, the product crystallizes from this solution after concentration and trituration. 1.5 liters of diisopropyl ether are added to the suspension of crystals, and the latter is stirred for one hour at room temperature, and filtered under suction. The product is dried over phosphorus pentoxide in a high vacuum.

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