Modeling cycloaddition reactions

Abstract

In this study, the selectivities in two types of cycloaddition reactions, namely Diels- Alder and 1,3-dipolar cycloadditions are investigated. In the first part, the diastereoselectivity in the hydrogen bonding assisted Diels-Alder reactions have been investigated by using different chiral dienes with achiral dienophiles with density functional methods. C9-substituted chiral anthracene templates are used to find out the role of chiral substituents and H-bonding on the product distribution ratio. As a the second study in this part, the π-facial selectivity induced by the presence of a chiral auxiliary in 1,4-substituted butadienes has been considered in order to rationalize the role of the chiral substituent on the stereoselectivity. In the second part, the conjugate addition/intramolecular nitrone dipolar cycloaddition is investigated with the use of density functional theory. The 1,3-dipolar intramolecular cycloaddition reaction of nitrone is analyzed in details. The most stable and energetically favored mechanism is searched for the interconversion of 6,5,5-tricyclic products to the 6,6,5-tricyclic structure which is the core intermediate to synthesize histrionicotoxins.