83602-18-0Relevant academic research and scientific papers
THE SYNTHESIS OF RIGID NORBORNYLOGS FOR THE PURPOSE OF STUDYING ORBITAL INTERACTIONS THROUGH BONDS
Paddon-Row, Michael N.,Cotsaris, Evangelo,Patney, Harish K.
, p. 1779 - 1788 (2007/10/02)
The synthesis of members of the series of rigid bichromophoric norbornylogs 4-8 is described.Dienes 4a and b were synthesized according to Scheme 1.Reductive dechlorination of 26-28 (Scheme 2) gave dienes 5b-d, respectively.Benzene annelation of the appropriate ene substrate, using tetrachlorodimethoxycyclopentadiene, as outlined in Scheme 3, gave the dibenzo compounds 6a-c.The dibromoquinodimethane intermediate 49 was trapped by the appropriate diene to give the bisnaphtho compounds 7a-c.The extended norbornylogs 8a and b were synthesized using a combination of metal catalyzed (2+2) cycloaddition of DMAD and (2+2+2) cycloaddition of quadricyclane to ene substrates (Scheme 5).The photoelectron spectra of some of the dienes are discussed in terms of through bond orbital interactions.
Orbital Interactions. XII. Product Studies and Competition Kinetic Measurements of the Birch Reduction of a Series of Hexahydrodimethanonaphthalenes and their Interpretation in Terms of Orbital Interactions Through Space and Through Bonds
Chau, Diem Dieu,Paddon-Row, Michael N.,Patney, Harish K.
, p. 2423 - 2446 (2007/10/02)
Relative rate constants for the Birch reduction (Li/ liq.NH3/ ButOH) of the three isomeric hexahydrodimethanonaphthalenes (3)-(5) and the octahydro analogues (10)-(13) were obtained and compared with those obtained for the reduction of norbornadiene and norbornene from an earlier study.Diene (5) was reduced almost 2000 times more rapidly than norbornene and 20000 times more rapidly than the monoene (13).Rate-enhancement factors for dienes (3) and (4) were less substantial but meaningful: 19 for (3) and 35 for (4) .These rate enhancements were attributed to the operation of ?* orbital interactions through space in diene (5) and to the presence of ?* orbital interactions through four bonds in dienes (3) and (4).The existence of a linear relationship between the natural logarithm of the rate of reduction of a substrate and its LUMO energy (obtained from either gas-phase electron affinities or ab initio MO calculations) supports this conclusion.The only-fair correlation of the above relationship was attributed to the neglect of other factors, such as the electronic structure and the geometry of the anion radical, which contribute to the overall rate of the Birch reduction.These two factors were explored by using PMO theory and ab initio MO calculations.In particular, full geometry optimizations (UHF, STO-3G basis set) on the anion radicals of norbornadiene (1) (C2v symmetry constraint) and norbornene (22) (Cs symmetry constraint) were carried out, and their geometries reported.Noteworthy is the strong pyramidalization of the olefinic centres of (1) and (22) in the endo direction.These pyramidalizations explain the observed stereoselective exo protonation of the anion radical of (1), and also the much faster rate of reduction of (1) compared with (5), since the pyramidalization im the anion radical of (5) is such to hinder protonation.The geometries of anion radicals appear to have a profound effect on rates, on stereoselectivity of protonation, and on the structures of the final products, and this is discussed in detail.The synthesis of the diene (3) is also described.
