Computational study on the mechanism of the three-component reaction of dimethylacetylene dicarboxylate and triphenylphosphine with 2-acetylbutyrolactone

Abstract

The molecular mechanism of the three-component reaction of triphenylphosphine, dialkyl acetylene dicarboxylate and 2-acetylbutyrolactone to synthesize the stabilized phosphorus ylide and 1,3-butadiene derivative via the intramolecular Wittig reaction, has been investigated using the density functional theory (DFT) method at the B3LYP/6-31G level of theory. Two possible reaction pathways have been characterized in detail to form the cyclobutene intermediate and in the next step; cyclobutene intermediate undergoes the conrotatory ring-opening reaction to produce the 1, 3-butadiene derivative along two possible pathways. The calculated results indicate that two pathways (pathway II and II-a) are the most energy favorable among all the pathways, so they occur more than the others.Moreover, the phosphorus ylide is more stable than the corresponding 1, 3-butadiene, demonstrating that the intramolecular Wittig reaction could not easily occur at room temperature which is in agreement with the experimental results.