金催化炔基苯并二??英环化合成8-羟基异香豆素的理论研究

Theoretical Study on Gold-catalyzed Cyclization of Alkynyl Benzodioxin to 8-Hydroxy-isocoumarin

Density functional theory（DFT） calculations were carried out on the gold-catalyzed cyclization of alkynyl benzodioxin to 8-hydroxy-isocoumarin reaction to show the molecular mechanism of the reaction. The conclusions obtained from this work are different from those in the previous experimental study. The results show that water molecule acts as both the reactant and the proton shuttle， and promotes the reaction with gold complexes under mild conditions. The nucleophilic addition site of water on the substrate is the C（sp³） atom on the side of the substrate far away from the oxabenzene ring， resulting in C（sp³）—O bond breaking in the substrate. The formation of new C—O bond and the cleavage of C—O bond in the substrate follow a step-by-step mechanism. The oxygen in the side-product acetone comes from the contribution of water in the reaction system. The regioselectivity of the reaction originates from the polarization of alkynyl π-electrons induced by substituents.