Mechanism of One-Pot Stereoselective Assembly of Spiroketal Derivatives from Cyclohexanone and Phenylacetylene in KOH/DMSO: a Quantum Chemical Study

The formation mechanisms of 15-[(Z)-phenylmethylidene]-7,14-dioxadispiro[5.1.5.2]pentadecane and the competitive formation of unsaturated ketones from cyclohexanone and phenylacetylene are studied using the B2PLYP-D2/6-311+G**//B3LYP/6-31+G* quantum chemical approach, taking into account solvation effects within the IEFPCM model. All stages of the assembly of dispiroketal and the stability of various conformers and isomers of the intermediates and the product are considered using the anionic model (ANIONGAS). Within the more detailed MONOPCM model, the activation barriers of the assembly of dispiroketal and the competing reaction of C-vinylation are evaluated. The obtained results of the quantum chemical calculations are in close agreement with the experimental data.