Mechanisms of the InCl3-Catalyzed Type-I, II, and III Cycloisomerizations of 1,6-Enynes
2014
Zhuo, Lian-Gang | Zhang, Ji-Ji | Yu, Zhi-Xiang
InCl₃-catalyzed cycloisomerizations of 1,6-enynes can give either type-I dienes and cyclohexenes (type-III dienes), or type-II dienes, depending on the substitutions in the substrates. Previously, we studied how the type-II diene products were generated and found that the real catalytic species for the cycloisomerizations is InCl₂⁺ (J. Org. Chem. 2012, 77, 8527–8540). In the present paper, we used density functional theory (DFT) calculations to reveal how the type-I and type-III dienes were generated. A unified model to explain how substituents affect the regiochemistry of type-I, II, and III cycloisomerizations has been provided. Experimental and computational investigation of the InCl₃-catalyzed cycloisomerization of 1,6-enynes with both substituents at the alkyne and alkene parts has also been reported in the present study.
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