135560-46-2Relevant academic research and scientific papers
Remote substituent effects on the oxymercuration of 2-substituted norbornenes: An experimental and theoretical study
Mayo,Orlova,Goddard,Tam
, p. 5182 - 5191 (2001)
The effect of a remote substituent on regioselectivity in the oxymercuration of 2-substituted norbornenes has been investigated experimentally and theoretically using density functional theory (DFT). Regioselectivities of 1:1 to 14:1 were observed with various 2-substituted norbornenes. Exo-2-substituted norbornenes always gave greater regioselectivities compared to the corresponding endo-2-substituted norbornenes. The effects of solvents on the regioselectivity have also been examined, and ethereal solvents were found to be the best choice giving the optimal yield and regioselectivity. The relative rate of oxymercuration was estimated by competition experiments. The least reactive substrate (X = OAc) gave the highest regioselectivity. According to DFT predictions, the increased difference between the reaction barriers that results in the greater regioselectivity is correlated directly with the larger polarity of the C=C double bond, which is attacked by the mercury and oxygen. A number of stable exo and endo conformers were predicted. All exo conformers show the same polarity of the double bond, while some endo conformers have a reversal of this polarity. All the conformers except those with the OAc substituent are very close in energy and thus should react. The existence of a mixture of endo conformers with the C=C double bond of opposite polarity clearly explains a decrease in regioselectivity for the endo species. The origin of the greatest regioselectivity for the OAc-2-norbornenes lies in the fact that the conformer with the largest polarity is notably lower in energy than others due to an internal C-H-O hydrogen bond.
Synthesis and functionalization of ROMP-based gradient copolymers of 5-substituted norbornenes
Dettmer, Christine M.,Gray, Maisha K.,Torkelson, John M.,Nguyen, SonBinh T.
, p. 5504 - 5512 (2004)
Gradient copolymers of exo-5-(benzyloxy)norbornene and exo-5-[(4-tert- butyl)benzyloxy]-norbornene were synthesized via ring-opening metathesis polymerization (ROMP). Kinetic studies revealed that the reactivity ratios of both monomers were close to unity. As predicted, this monomer pair did not result in copolymers with significant gradients under batch polymerization conditions. However, semibatch conditions resulted in copolymers with sizable gradients whose shape was independent of the rate of addition. Addition of the monomers simultaneously via a dual and opposite ramping strategy led to a 50/50 copolymer with an exceptionally linear gradient. These gradient copolymers were further functionalized via hydrogenation, bromination, and bromoalkoxylation.
