Mechanistic Investigation on Rhodium(III)-Catalyzed Cycloaddition of 2-Vinylphenol Derivatives with Ethyne or Carbon Monoxide by DFT Study

铑(III)催化2-乙烯基苯酚衍生物与乙炔或一氧化碳的环加成反应机理研究

Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives.In this work,we conducted a computational study of two competitive mechanisms in which the carbon atom of acetylene or carbon monoxide attacked and inserted from two different directions of the six-membered ring reactant to clarify the principle characteristics of this transformation.The calculation results reveal that:(i)the insertion process of alkyne or carbon monoxide is the key step of the reaction;(ii)for the(5+2)cycloaddition reaction of acetylene,higher energy is required to break the Rh−O bond of the reactant,and the reaction tends to complete the insertion from the side of the Rh−C bond;(iii)for the(5+1)cycloaddition of carbon monoxide,both reaction paths have lower activation free energy,and the two will generate a competition mechanism.