DFT study on the mechanism of InBr3-catalyzed [2+2] cycloaddition of allyltrimethylsilane with alkynones
Density functional theory calculations at the M06-2X level were done to study the reaction mechanism and regioselectivity for the [2+2] cycloaddition of allyltrimethylsilane with alkynones using InBr₃ as the catalyst. The solvent effect was described by the single-point calculations with SMD model in 1,2-dichloroethane. The calculation results prove that the InBr₃-catalyzed cycloaddition of allyltrimethylsilane to alkynones takes place through two possible pathways and get selective cyclobutenone products. The reaction involves two main steps: attack of unsaturated carbon atoms of the alkynone by the π electrons of allyltrimethylsilane and a closed-loop process. The process of forming cyclobutenone product of silicon in the 2-position of the ketone group is more favored and the barrier is 15.5 kcal/mol, while the energies for the cyclobutenone of 3-position product are relatively high of 21.2 kcal/mol. In addition, we calculated the catalytic activity of the InX₃(X=Cl, Br, I) catalyst for this cycloaddition. This is a good explanation for the experimental data thatInBr₃ and InI₃ would be the most effective catalysts.
Volume 134, 2022
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