The mechanism of the cyclization of allylic alkynoates catalyzed by PdCl2 was studied by means of the density functional theory (DFT). The intermediates and the transition states for this reaction were optimized completely at the B3LYP/6-311G(d,p) level. As shown, the cyclization is exothermic and mainly undergoes the halopalladation of alkyne, the intramolecular olefin insertion to palladium-vinyl intermediate, and the quenching of the carbon-palladium bond by the β-heteroatom elimination. The chirality-determined step is the intramolecular olefin insertion, and the rate-controlled step is the β-heteroatom elimination. The dominant products predicted theoretically are (Z,R)-α-methylene-γ-butyrolactone derivative which is in agreement with the experimental results.

Key words: cyclization of allylic alkynoates, β-heteroatom elimination, density functional theory, reaction mechanism