General Method for the Preparation of Electron-Deficient Imidazo[1,2-a]pyridines and Related Heterocycles
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- 作者：Ivar M. McDonald ; Kevin M. Peese
- 刊名：Organic Letters
- 出版年：2015
- 出版时间：December 18, 2015
- 年：2015
- 卷：17
- 期：24
- 页码：6002-6005
- 全文大小：296K
- ISSN：1523-7052
文摘
A new annulation method for the preparation of the imidazo[1,2-a]pyridine ring system under mild conditions is presented. Treatment of a 2-aminopyridine with a dimethylketal tosylate in acetonitrile at elevated temperature (80鈥?40 掳C) in the presence of catalytic Sc(OTf)3 provides the imidazo[1,2-a]pyridine product in good yield. The annulation method is broadly applicable to electron-poor 2-aminopyridines and displays a complementary profile to the classic preparation of the imidazo[1,2-a]pyridine ring system by reaction of a bromoketone with electron-rich and -neutral substrates. The scope of the process and mechanistic considerations are discussed.