Pyramidalized Olefins: Ab Initio Study and X-ray Structure Determination of Bicyclo[2.2.2]octadienes

Pyramidalized Olefins: A DFT Study of the Homosesquinorbornene and Sesquibicyclo[2.2.2]octene Nuclei

“…The diene 28 displays a modest pyramidalization (ψ = 1.8°) while both 29 and 32 are pyramidalized to a greater extent (ψ= 5.7 and 8.5°, respectively). In each of 28 , 29 , and 32 the butterfly bending is, as expected, − in the exo (to the bicyclo[2.2.2]octadiene moiety) direction. The diminished pyramidalization in 28 is again attributed to the unfavorable steric interaction between the proximate ethano bridges (H- - - H distance, 3.139 Å).…”

“…Norbornene and its derivatives, especially those resulting from syn fusion of another norbornyl nucleus, e.g., syn -sesquinorbornene ( 1 ), have double bonds that are considerably pyramidalized in the endo direction. , The double bonds in bicyclo[2.2.2]octadienes are similarly pyramidal, but, in contrast with the norbornenes, the butterfly bending is in the exo direction and the degree of pyramidalization is somewhat less. − In comparison with the sesquinorbornenes, there are few structural studies of compounds with a bicyclo[2.2.2]octyl unit fused to the bicyclo[2.2.2]octene nucleus, sesquibicyclo[2.2.2]octenes, or the norbornene nucleus, homosesquinorbornenes. X-ray crystallography revealed that the double bond of sesquibicyclo[2.2.2]octene ( 2 ) and a symmetrically cage-substituted derivative, not surprisingly in light of their symmetry, are planar .…”

Noncovalent Interactions in Succinic and Maleic Anhydride Derivatives

“…There, one of the carbonyl oxygen atoms of one molecule points to the inner region of a neighboring molecule, with the donor atoms slightly displaced from the ring centroid toward a carbonyl carbon ( d C···O = 2.93 Å; Σ r vdW = 3.27 Å). Another interesting example is the dimer found in the crystal structure of bicyclo(2.2.2)­octa-2,5-diene-2,3-dicarboxylic anhydride (GIQRAZ, Figure ), in which there are two short O···C contacts at 2.96 and 3.18 Å (Σ r vdW = 3.27 Å). Those contacts support two C–H···O contacts at distances (2.87 and 3.02 Å) longer than the sum of the corresponding van der Waals radii (Σ r vdW = 2.70 Å).…”

7-Oxanorbornene cycloadducts. X-Ray, molecular orbital and photoelectron spectroscopic study †

“…27 Applicability of this theoretical method to other strained systems with nonplanar double bonds, including those composed of 7-oxanorbornene subunits, has been also discussed by us 28 and other research groups. 29 Similarly, investigations of the electronic structure of 7-oxanorbornene derivatives have been the subject matter of several previous photoelectron spectroscopic studies. [30][31][32][33][34] The aim of PE investigation of epoxides 1-3 presented here was to extend our earlier work directed toward understanding the ability of rigid polycyclic spacers to transmit long range π-electron and lone pair interactions.…”