89856-87-1Relevant academic research and scientific papers
π*/σ* Orbital mixing. Synthesis and excited-state studies of 7-chloro-2-(trimethylsiloxy)norbornene and C-chloro-3-methoxy-exo-tricyclo[5.2.1.02,6]dec-3-ene
Nash, John J.,Carlson, Dean V.,Kasper, Annette M.,Love, Dan E.,Jordan, Kenneth D.,Morrison, Harry
, p. 8969 - 8979 (2007/10/02)
anti-7-Chloro-2-(trimethylsiloxy)norbornene (AntiCl) and syn-7-chloro-2-(trimethylsiloxy)norbornene (SynCl) as well as the epimeric exo-9- and endo-9-chloro-3-methoxy-exo-tricyclo[5.2.1.02,6]dec-3-ene (GExoCl and GEndoCl, respectively) have been synthesized, their electronic absorption and electron transmission (ET) spectra have been determined and their photochemistry at 254 nm has been studied. MO calculations have been carried out to aid in the interpretation of the spectra. In contrast to exo-6-chloro-2-(trimethylsiloxy)norbornene (ExoCl), the calculations show that the LUMO's of AntiCl and SynCl contain relatively little C-Cl σ* character, similar to endo-6-cbloro-2-(trimethylsiloxy)norbornene (EndoCl). This is consistent with the relatively low (compared to ExoCl) quantum efficiencies of disappearance for these compounds (Φdis(AntiCl) = 0.0072, Φdis(SynCl) = 0.0027). The ET spectra reveal that the π* levels in all of the chloro-substituted compounds are appreciably stabilized relative to that of 2-(trimethylsiloxy)-norbornene (TMSNB). However, a natural bond orbital (NBO) analysis shows that much of this stabilization derives from electric field (i.e., inductive) effects. Only in the case of ExoCl does the NBO analysis indicate sizable through-space (TS) and through-bond (TB) coupling between the π* and C-Cl σ* orbitals. Ab initio calculations on the extended chloro enol ethers GExoCl and GEndoCl (i.e., -y-chlorides) show that the LUMO's of these molecules contain a small amount of C-Cl σ* character. In addition, an NBO analysis shows that there are small TB interactions between the enol ether π* and C-Cl σ* orbitals in both GExoCl and GEndoCl. However, photoinduced cleavage of the C-Cl linkage following π* → π* excitation at 254 nm is not observed in these compounds.
Stereochemistry of acid-catalyzed cleavage of 3-chloro- and 3-bromonortricyclene in deuterated medium. Evidence for edge protonation of nortricyclenes
Werstiuk, Nick Henry,Timmins, George,Cappelli, Frank Peter
, p. 1709 - 1724 (2007/10/02)
Cleavage of 3-chloronortricyclene (4c) and 3-bromonortricyclene (4d) occurs faster than solvolysis in D2SO4-DOAc at 70-75 deg C and yields syn-7-, anti-7-, exo-5-, and endo-5-halo-exo-2-norbornyl acetates as products.That the 7-chloroacetates comprise 70percent of the reaction mixture, that 30percent of the 5-chloro-exo-2-norbornyl acetates which comprised 28percent of the reaction mixture are derived via rearrangement of the syn-7- and anti-7-chloronorbornyl cations, and that the deuterium at C-6 is at least 90percent stereochemically pure endo is evidence that cleavage of the bond farthest removed from the electron withdrawing halogen is preferred 5:1 over the other bonds of the three-membered ring.The stereochemistry of the ring-opening is rationalized on the basis of cleavage via edge-deuteronation with formation of classical halocations as intermediates.The location of deuterium in the 5-halo-exo-norbornyl acetates is used to define the pathways whereby the 5-haloacetates are formed.This study also establishes that C-6 endo deuterated 7-chloro- and 7-bromo-exo-2-norbornyl brosylates can be synthesized from the corresponding 3-halonortricyclenes.
