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Abstract <p>The article presents a quantum-chemical analysis of the mechanism of formation of dispiroketals from 2-methylcyclohexanone and phenylacetylene in a superbasic KOH/DMSO medium. The conformations of the starting ketone, the formation pathways of intermediate products and isomers, and the energy barriers of the key stages were studied by the B2PLYP-D2/6-311+G**//B3LYP/6-31+G* methods. It was established that the reaction occurs in three stages: nucleophilic ethynylation of ketone, formation of semiketal, and intramolecular <i>O</i>-vinylation. The rate-determining process is the two-stage process of addition of the second ketone molecule and subsequent <i>O</i>-vinylation. Of the eight possible diastereomers, only three are localized (<i>SSSS</i>, <i>RSSR</i>, <i>SSSR</i>), the final ratio of which is 7 : 2 : 1. The predominance of the <i>SSSS</i> isomer is associated with the thermodynamic stability and kinetically advantageous formation of the preceding alkoxide ion.</p>

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Quantum-Chemical Study of the Mechanism of Assembly of Spiroketal Derivatives from 2-Methylcyclohexanone and Phenylacetylene in a KOH/DMSO Medium

  • 期刊论文

  • 发表日期：

    2026年3月1日

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  • V. B. Orel,
  • A. A. Manzhueva,
  • N. M. Vitkovskaya

摘要

Abstract

The article presents a quantum-chemical analysis of the mechanism of formation of dispiroketals from 2-methylcyclohexanone and phenylacetylene in a superbasic KOH/DMSO medium. The conformations of the starting ketone, the formation pathways of intermediate products and isomers, and the energy barriers of the key stages were studied by the B2PLYP-D2/6-311+G**//B3LYP/6-31+G* methods. It was established that the reaction occurs in three stages: nucleophilic ethynylation of ketone, formation of semiketal, and intramolecular O-vinylation. The rate-determining process is the two-stage process of addition of the second ketone molecule and subsequent O-vinylation. Of the eight possible diastereomers, only three are localized (SSSS, RSSR, SSSR), the final ratio of which is 7 : 2 : 1. The predominance of the SSSS isomer is associated with the thermodynamic stability and kinetically advantageous formation of the preceding alkoxide ion.