Theoretical Study of the Diels-Alder Reaction in the Synthesis of Abietane Diter

Abstract: Density Functional Theory(DFT),at the B3LYP/6-311 G(d,p)level of theory and Moller-Plesse Theory (MP2/6-311G (d,p)) has been performed to study the mechanism, potential energy surface of the Diels-Alder reaction in the Synthesis of abietane diterpenes. The obtained results indicate that the reaction is concerted and synchronous processes. The transannular product is formed via a six-member ring transition state, yield of the endo product is higher. And finally, the enthalpie and activation energie of the reaction are given respectively.The reaction is exothermic,which accords well with experimental observation.

Keywords: transannular Diels-Alder reaction;abietane diterp- enes;Density functional theory (B3LYP /6-311G(d,p;MP2/6-311 G(d,p)

I. INTRODUCTION

The transannular Diels-Alder (TADA) reaction is unparelleled in its ability to generate high degree of stereochemical and architectural complexity in a single tranformation,which has been pay attention by people to its important role in the synthesis of many terpene natural products[1,2]. In the past few years,the TADA reaction has emerged as powerful tool to approach polycyclic diterpenes having various special pharmacological activities including antitumor, by changing groups and number of atoms. Theoretical study of the TADA reaction in the synthesis of abietane diterpenes in domestic and abroad has also reported fresh[3,4]. In this work,the mechanism of the Diels-Alder reaction in the synthesis of abietane diterpenes is investigated by DFT (B3LYP/6-31G*) and MP2 methods.The success of this research project can make up shortage of experiments, which can offer certain theory foundation for the development of the synthesis of abietane diterpenes[5,6].

II. COMPUTATIONAL METHODS

All calculations are carried out on East China Jiaotong University workstations, using the GAUSSIAN03 software suite[7]. The energies and geometries of the reactant, product as well as of the transition structure (TS1) were performed using the B3LYP exchange-correlation functionals, together with the standard 6-311G*(d,p) basis set. After optimization,the stationary points were characterized by frequency calculations in order to verify that the TSs have one and only one imaginary frequency.

The following conclusions can be drawn from our calculations.The reaction is concerted and synchronous processes.The transannular product is formed via a six-member ring transition state, yield of the endo product is higher.The reaction is exothermic,which accords well with experimental observation.

Acknowledgment

We are grateful for the tireless efforts of our project team and support of Tangshan scientific and technical project Foundation. This work is partially supported by Tangshan scientific and technical project (12120212A).

References

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