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Dibenzocycloheptanones construction through a removable P-centered radical: synthesis of allocolchicine analogues
Chemical Science  (IF9.825),  Pub Date : 2021-11-09, DOI: 10.1039/d1sc05404j
Yan Zhang, Zhenzhi Cai, Julia Struwe, Chanchan Ma, Wangyu Zeng, Xinyi Liao, Min Xu, Lutz Ackermann

Dibenzocycloheptanones containing a tricyclic 6–7–6-system are present in numerous biologically active natural molecules. However, the simple and efficient preparation of derivatives containing a dibenzocycloheptanone scaffold remains difficult to date. Herein, we report a versatile strategy for the construction of these challenging seven-membered rings using a 7-endo-trig cyclization which is initiated by a phosphorus-centered radical. This approach provides a step-economical regime for the facile assembly of a wide range of phosphorylated dibenzocycloheptanones. Remarkably, we also have devised a traceless addition/exchange strategy for the preparation of dephosphorylated products at room temperature with excellent yields. Therefore, this protocol allows for the concise synthesis of biorelevant allocochicine derivatives.