Divergent Synthesis of Functionalized Spiroindanediones via CdI2/MgI2-Catalyzed Multiple Cyclocondensation Modes
Wen-Hui Zhang1,2, Ying-Mei Li1, Ying Zhou1,2
1College of Pharmacy, Guizhou University of Traditional Chinese Medicine, Guiyang550025, P. R. China.
Abstract:
Divergent synthesis enables rapid construction of structurally diverse compound libraries from the same universal substrates and is a current research hotspot. Here, the self-(3 + 2), (2 + 1), and (1 + 1 + 1) cyclocondensations of 2-arylidene-1,3-indanediones 1 were realized, respectively, by simply tuning the catalyst species and reaction temperature. The protocols enable access to various spiroindanediones 2, 4, and 5 in good to excellent yields (up to 91%). The products 2 can be further transformed into novel functionalized derivatives 3 by placing them in methanol/methanol-d4 (up to 89% yield, all >20:1 dr). Two core catalytic cyclocondensation pathways are proposed, including the CdI2-catalyzed (3 + 2) cyclocondensation initiated by O-Michael addition and the MgI2-promoted (2+1) cyclocondensation triggered by Michael addition.
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The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable, the...

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