Understanding the Mechanism and Selectivities of the Reaction of Meta-Chloroperbenzoic Acid and Dibromocarbene with β-Himachalene: A DFT Study

• Published in: Heteroatom chemistry 2020, Vol.2020 (2020), p.1-8
• Main Authors: Abdennouri, Mohamed, Zgou, Hssaine, Benharref, Ahmed, Sadiq, M’hamed, Barka, Noureddine, Hammal, Redouan, Lemdek, El Mokhtar, Khnifira, Malika, El Hamidi, Sana, Chekroun, Ahmed
• Format: Article
• Language: English
• Subjects: Chemistry; Density functional theory; Exothermic reactions; Hessian matrices; Mathematical analysis; Oils & fats; Selectivity; Stereoselectivity
• ISSN: 1042-7163; 1098-1071
• DOI: 10.1155/2020/8885991

This study was performed to understand the site selectivity in the reaction between β-himachalene and meta-chloroperbenzoic acid (m-CPBA) in the first step followed by the addition of dibromocarbene (CBr2) to the main monoepoxidation product Pα formed in the first reaction. Calculations were performed using the Becke three-parameter hybrid exchange functional and the Lee–Yang–Parr correlation functional (B3LYP) with the 6-311 + G (d, p) basis set. Transition states were located by QST2, and their highlighting was validated by the existence of only one imaginary frequency in the Hessian matrix. The action of m-CPBA on β-himachalene was analyzed on the two double bonds of β-himachalene whose theoretical calculations show that the attack affects the most substituted double bond on α side containing hydrogen of ring junction. The obtained Pα product thereafter treated with dibromocarbene leads via an exothermic reaction to the six-membered ring double bond position of α-monoepoxide. The major products Pαα are kinetically and thermodynamically favored with a high stereoselectivity in perfect correlation with the experimental observations.