Facial Selectivity in the Diels–Alder Reactions of 2,2‐Disubstituted Cyclopent‐4‐ene‐1,3‐dione Derivatives and a Computational Examination of the Facial Selectivity of the Diels–Alder Reactions of Structurally Related Dienes and Dienophiles

Synthesis of Angular Triquinane and [4.3.3]Propellane Derivatives via Ring‐Rearrangement Olefin Metathesis

“…The enone 13 on reaction with cyclopentadiene gave two cycloadducts 14 and 15 in 4 : 1 ratio respectively (Scheme 1). [11] The structures of endo and exo-adducts were established by NMR spectroscopic and HRMS data and further supported by single crystal X-ray diffraction studies (Figure 3). Having both these isomers 14 and 15 in hand, we first attempted ROM of exo isomer 15 using Grubbs (GÀ I, G-II) catalysts and we realized that the yield of compound 16 is more with GÀ I catalyst than with G-II catalyst.…”

“…The enone 13 on reaction with cyclopentadiene gave two cycloadducts 14 and 15 in 4 : 1 ratio respectively (Scheme 1). [11] The structures of endo and exo-adducts were established by NMR spectroscopic and HRMS data and further supported by single crystal X-ray diffraction studies (Figure 3).…”

Computational Examination of (4 + 3) versus (3 + 2) Cycloaddition in the Interception of Nazarov Reactions of Allenyl Vinyl Ketones by Dienes

“…In an effort to identify what controls extended versus compact (4 + 3) cycloadditions and (4 + 3) versus (3 + 2) cycloaddition selectivities, an examination of the deformation energies for the reactants and the interaction energies at the various transition states was undertaken. Applications of such analyses by ourselves and by others have been successful in clarifying the origins of selectivity in Diels–Alder and other cycloaddition reactions. The difference in energy (Δ E ) between the diene in its lowest-energy conformation and the isolated diene in its transition state geometry is the “diene deformation energy.” The corresponding energy for the oxyallyl cation is the “oxyallyl cation deformation energy.” Subtraction of the two deformation energies from the activation energy (Δ E ‡ ) gives the “interaction energy.” The deformation and interaction energies of the transition states in the concerted (4 + 3) cycloaddition and stepwise pathways studied above are provided in Figure .…”

“…Thus, the interaction energies, which could include both the strong attractive as well as some repulsive interactions, overwhelm the contributions of deformation. This is in contrast with analyses of Diels–Alder reactions in which the interaction energies were smaller and fairly constant, but the deformation of the diene correlated strongly with the selectivity.…”