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Four-Component Bicyclization Approaches to Skeletally Diverse Pyrazolo[3,4-b]pyridine Derivatives
- Tu, Xing-Jun, Hao, Wen-Juan, Ye, Qin, Wang, Shuang-Shuang, Jiang, Bo, Li, Guigen, Tu, Shu-Jiang
- Journal of organic chemistry 2014 v.79 no.22 pp. 11110-11118
- aromatic amines, chemical reactions, chemical structure, microwave treatment, organic chemistry, pyridines, quinolones, stereoselectivity
- A novel four-component bicyclization strategy has been established, allowing a flexible and practical approach to 37 examples of multicyclic pyrazolo[3,4-b]pyridines from low-cost and readily accessible arylglyoxals, pyrazol-5-amines, aromatic amines, 4-hydroxy-6-methyl-2H-pyran-2-one, and cyclohexane-1,3-diones. The polysubstituted cyclopenta[d]pyrazolo[3,4-b]pyridines were stereoselectively synthesized through a microwave-assisted special [3+2+1]/[3+2] bicyclization with good control of the spatial configuration of exocyclic double bonds. The novel [3+2+1]/[2+2+1] bicyclization resulted in 17 examples of unreported pyrazolo[3,4-b]pyrrolo[4,3,2-de]quinolones. Reasonable mechanisms for forming two new types of multicyclic pyrazolo[3,4-b]pyridines are also proposed.