Study on the peri- and stereoselectivity of cycloaddition reaction of disulfonyl diene with cyclopentadiene by computational methods

Synthesis and properties of sulfonylated 1,3-dienes have received considerable attention over the years [1]. One of the characteristic properties of these dienes is their dual behavior in [4+2] cycloaddition reactions. They can reacted undergo cycloaddition reactions with a variety of olefins ranging from electron-deficient to electron rich dienophiles [2]. 2,3-(ethylene disulfonyl)-1,3-butadiene (1) is a very reactive diene which can react with a number of alkenes in [4+2] cycloaddition reactions. It is important to note that 1 as electron-deficient, readily reacted with both electron-rich and electron-poor dienophiles. The aim of this work was to study the mechanism of peri- and stereoselectivity of the cycloaddition reactions of disulfone 1 with 2,3-dimethylbutadiene 2 by DFT method at different levels. Theoretical calculations indicated two pathways for each reactions, endo and exo which endo paths are more reactive than exo ones. The disulfone 1 can reacts with 2,3-dimethylbutadiene 2 in [2+4] cycloaddition reaction with the lower energy barrier than [4+2] cycloaddition reaction. The dienophilic character of 1 is more pronounced than its dienic character in these DA reactions. Moreover, an analysis of the reactivity indices and Parr functions for the reactants allows us to provide an explanation of the periselectivity of these cycloaddition reactions.