Studies on Pyrazolo [3, 4-d] pyrimidine Derivatives. XVI. Preparation of Reissert Compounds from Condensed Pyrimidine Systems Catalyzed by Lewis Acids

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Among various Lewis acids, aluminium chloride (AlCl₃) was the most effective catalyst for the formation of the Reissert compound (2_1a, 5-benzoyl-4, 5-dihydro-1-phenyl-1H-pyrazolo [3, 4-d] pyrimidine-4-carbonitrile) of 1-phenyl-1H-pyrazolo [3, 4-d] pyrimidine (1₁) by using benzoyl chloride and trimethylsilyl cyanide (TMSCN) in anhydrous methylene chloride (CH₂Cl₂).
Application of this method to derivatives of the following condensed pyrimidines, 1H-pyrazolo [3, 4-d] pyrimidine (1), 9H-purine (3), 3H-1, 2, 3-triazolo [4, 5-d] pyrimidine (5), and quinazoline (7), gave the corresponding new series of Reissert compounds (2, 4, 6, 8, and 9), which could not be prepared by the standard method using potassium cyanide and acid chloride in aqueous media.