Theoretical study on the mechanism and selectivity of asymmetric cycloaddition reactions of 3-vinylindole catalyzed by chiral N,N'-dioxide-Ni(II) complex

exo/endo Selectivity Control in Diels–Alder Reactions of Geminal Bis(silyl) Dienes: Theoretical and Experimental Studies

“…In addition, predominant exo selectivity cycloadducts could also be obtained by adjusting the electronic properties of the reactants. For example, a favorable π–π stacking between the conjugated diene and dienophile could stabilize exo transition states to realize excellent diastereofacial selectivity . The fluorine substituent effect could affect the kinetics and stereochemistry, leading to the formation of an exo adduct with high steroeselectivity in the DA reaction of fluorinated dienophiles. , …”

“…The stress on the C β substituent and steric as well as electrostatic repulsion from the electron-withdrawing group of the dienophile in endo transition states diminished the preference for the endo pathway, increasing the likehood of the exo pathway. Our previous calculations for a DA reaction between 3-vinylindole and methyleneindolinone indicated that a “pocket-like” chiral cavity constructed by a chiral N , N ′-dioxide Ni­(II) catalyst enhanced the exo diastereofacial selectivity significantly by maximizing the overlap of the two indole rings of the substrates, leading to high exo selectivity . Fernández and co-workers studied the effect of Lewis bulkiness on endo / exo selectivity in B­(C 6 F 5 ) 3 - and AlCl 3 -mediated DA reactions between acyclic dienes and α,β-enals.…”

“…For example, a favorable π−π stacking between the conjugated diene and dienophile could stabilize exo transition states to realize excellent diastereofacial selectivity. 34 The fluorine substituent effect could affect the kinetics and stereochemistry, leading to the formation of an exo adduct with high steroeselectivity in the DA reaction of fluorinated dienophiles. 35,36 With respect to the extensively studied endo selectivity DA reaction, theoretical investigations on the exo cycloadduct DA reaction are limited.…”

“…35,36 With respect to the extensively studied endo selectivity DA reaction, theoretical investigations on the exo cycloadduct DA reaction are limited. 10,34,37 Corey et al employed a molecular mechanics (MM) method to study the conformation of dienes in the DA reaction between 1,3-dienes and 2-cycloalkenones. 10 Steric repulsion between the aromatic ring of a bicyclic diene and an α,β-enone favored the skewed diene geometry to form an exo transition state.…”

“…Our previous calculations for a DA reaction between 3-vinylindole and methyleneindolinone indicated that a "pocket-like" chiral cavity constructed by a chiral N,N′dioxide Ni(II) catalyst enhanced the exo diastereofacial selectivity significantly by maximizing the overlap of the two indole rings of the substrates, leading to high exo selectivity. 34 Fernańdez and co-workers studied the effect of Lewis bulkiness on endo/exo selectivity in B(C 6 F 5 ) 3 -and AlCl 3 -mediated DA reactions between acyclic dienes and α,β-enals. The exo selectivity for the bulky B(C 6 F 5 ) 3 catalyst came from the interplay between the less destabilizing strain and the stronger interaction energy between deformed reactants along the entire reactant coordinate.…”