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Paper | Regular issue | Vol 102, No. 1, 2021, pp.69-80
Published online, 13th November, 2020
DOI: 10.3987/COM-20-14356
Practical Synthesis of 1-Substituted 5-Aminopyrazolo[4,3-d]pyrimidin-7-ones Using Intramolecular Friedel–Crafts Type Cyclization and Its Application to the Synthesis of Pharmaceutically Active Compounds

Takashi Goi,* Tetsuji Matsudaira, and Koichi Fukase*

*Sohyaku. Innovative Research Division, Mitsubishi Tanabe Pharma Corporation, 1000, Kamoshida-cho, Aobaku, Yokohama, 227-0033, Japan


Intramolecular Friedel–Crafts type cyclization is known as an efficient method of synthesizing fused bicyclic pyrimidones. However, the synthesis of 1-substituted pyrazolo[4,3-d]pyrimidin-7-ones using this cyclization method has not been achieved. Herein, we describe the synthesis of various 1-substituted pyrazolo[4,3-d]pyrimidin-7-ones using practical intramolecular Friedel–Crafts type cyclization, which was carried out in N, N-dimethylformamide in the presence of chlorotrimethylsilane. A hypoxia-inducible factor prolyl hydroxylase domain (HIF-PHD) inhibitor was efficiently synthesized by this method.