Pericyclic reactions overview

In the present chapter, we review the pericyclic reactions studied with DFT methods to date. Local, nonlocal, and hybrid DFT methods have been used to study the parent systems of the most important pericyclic reactions. These results are compared with results of Hartree-Fock theory, post-Hartree-Fock calculations, and available experimental data. Our aim is to provide an overview... 

This review has provided an overview of the studies of pericyclic reaction transition states using density functional theory methods up to the middle of 1995. Since the parent systems for most of the pericyclic reaction classes have been studied, a first assessment of DFT methods for the calculation of pericyclic transition structures can be made. 

Most organic reactions result from the union of an electron-rich nucleophile (Nu ) with an electron-poor electrophile (E+). (Exceptions to this generalization include radical reactions, pericyclic reactions, and reactions mediated by organometaUic species.) In order to properly plan for an organic synthesis, one must be familiar with commonly used electrophiles and nucleophiles. Presented in this section is an overview of such species, all of which are either commercially available or readily prepared. These nucleophiles and electrophiles will be employed throughout this book as their reactions and uses in synthesis are presented in detail in subsequent chapters. 

We then present ab initio molecular orbital theory. This is a well-defined approximation to the full quantum mechanical analysis of a molecular system, and also the basis of an array of powerful and popular computational approaches. Molecular orbital theory relies upon the linear combination of atomic orbitals, and we introduce the mathematics and results of such an approach. Then we discuss the implementation of ab initio molecular orbital theory in modern computational chemistry. We also describe a number of more approximate approaches, which derive from ab initio theory, but make numerous simplifications that allow larger systems to be addressed. Next, we provide an overview of the theory of organic TT systems, primarily at the level of Hiickel theory. Despite its dramatic approximations, Hiickel theory provides many useful insights. It lies at the core of our intuition about the electronic structure of organic ir systems, and it will be key to the analysis of pericyclic reactions given in Chapter 15. 

Diterpenes are among the most abundant terpenoids on the planet. Although significant advancements have been made, the biosynthesis of diterpenes is not fully elucidated. In this chapter, a general overview of the biosynthesis of diterpenes and selected applications of pericyclic reactions for the synthesis of complex diterpenes will be presented. 

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