21516-65-4Relevant academic research and scientific papers
Stereospecific nucleophilic trapping of encounter complexes between photoexcited 1-cyanonaphthalene and norbornadiene
Weng, Hengxin,Roth, Heinz D.
, p. 101 - 108 (1998)
Photo-induced electron donor-acceptor reactions between 1-cyanonaphthalene (CNN) and norbornadiene (N) generate products of several structure types. Methanol adducts (1-3) formed in polar solvents are rationalized via the radical cation, N+., and stereospecific (exo-) nucleophilic attack by methanol. In less polar solvents, CNN and N form [2 + 2]-cycloadducts, exclusively on the exo-face of N. In non-polar solvents containing methanol, CNN, N and methanol combine to form 1:1:1 adducts, containing the sensitizer on the endo- and the methoxy groups on the exo-face. The formation of these products is rationalized via the trapping of encounter complexes of different geometries. Any rearrangement of the norbornenyl system can be eliminated, since neither tricyclyl nor 7-methoxynorbornenyl structures are formed. Apparently, the alcohol captures an endo-encounter complex of CNN and N by attack from the exo-face, similar to the attack of methanol on N+..
Electron Transfer Photochemistry of Norbornadiene and Quadricyclane. Nucleophilic Capture of Radical Cations, Free-Radical Rearrangements, and Hydrogen Abstraction
Weng, Hengxin,Roth, Heinz D.
, p. 4136 - 4145 (1995)
The photoinduced electron donor-acceptor reactions between norbornadiene (N) or quadricyclane (Q) and acceptor/sensitizers generate products of several structure types, depending on the nature of sensitizers and solvents.Irradiation of 1,4-dicyanobenzene (DCB) in acetonitrile/methanol leads to methanol adducts 2 and 3, NOCAS products 4-7, and two acetonitrile adducts 8 and 9, which are formed only from N.The products are rationalized via stereospecific nucleophilic attack by methanol on the radical cations, N(.+) and Q(.+), from the exo-face.The resulting free radicals, exo-3-methoxybicyclohept-5-en-2-yl (N(.+) -> CH3O-B(.)) and anti-5-methoxytricyclo2,6>heptan-3-yl (Q(.+) -> CH3O-C(.)) undergo rapid molecular rearrangements to CH3O-C(.) and syn-7-methoxybicyclohept-5-en-2-yl, (CH3O-E(.)), respectively, before forming products 2-7.The methanol adducts 2 and 3 are ascribed to hydrogen abstraction by CH3O-C(.) and CH3O-E(.), most likely due to the insufficient reducing ability of DCB(.-).The abstraction reaction is supported by isotropic labeling studies and by acetonitrile adducts 8 and 9 formed by attack of (.)CH2CN on N.The reduced singlet energy of 1-cyanonaphthalene (CNN) causes the electron transfer from N to be less favorable, whereas the reducing ability of CNN(.-) is increased.The reaction leads to methanol adducts 1-3, -cycloadducts, and several 1:1:1 adducts of CNN, N, and methanol.The formation of methanol adducts is initiated by nucleophilic capture of the radical cations; isotopic labeling studies suggest a competition between hydrogen abstraction and reduction/protonation mechanisms.
Rh(III)-photosensitized interconversion of norbornadiene and quadricyclane
Sluggett, Gregory W.,Turro, Nicholas J.,Roth, Heinz D.
, p. 8834 - 8838 (2007/10/03)
The utility of two Rh(III) diimine complexes, Rh(phen)33+ and Rh(phi)2(phen)3+ (phen = 1,10-phenanthroline, phi = 9,10-phenanthrenequinone diimine), as sensitizers for the interconversion of norbornadiene (N) and quadricyclane (Q) has been investigated using steady-state photochemical and laser flash photolysis (LFP) techniques. Irradiation of acetonitrile solutions of Rh(phen)33+ and N causes slow conversion to Q. The reaction is reversible; irradiation of Rh(phen)33+ in the presence of Q leads to N. Irradiation of acetonitrile solutions of Rh(phi)2(phen)3+ and Q yields N. However, this reaction is irreversible; irradiation of the Rh-(III) complex in the presence of N fails to afford Q. Irradiation of methanol solutions of either Rh(III) complex in the presence of N or Q affords minor amounts of two methanol-C7 adducts but fails to quench the N-Q interconversion reaction. The results are consistent with N-Q interconversion via an exciplex intermediate. The Rh(III)-sensitized deazatization of two cyclic azoalkane derivatives (Azo-N, Azo-Q) of N and Q was also investigated. Deazatization was achieved by Rh(phen)33+ but not Rh(phi)2(phen)3+ sensitization. The results are consistent with a mechanism involving triplet energy transfer, but the involvement of exciplex intermediates cannot be ruled out. Bimolecular rate constants for quenching of the Rh(III) excited states by N, Q, Azo-N, and Azo-Q were determined by LFP.
Metal Ion Photoinitiated Addition of Acetonitrile and Methanol to Olefins
Bruno, Joseph W.,Marks, Tobin J.,Lewis, Frederick D.
, p. 5580 - 5585 (2007/10/02)
Irradiation of norbornene and silver or thallium trifluoromethanesulfonate in acetonitrile solutions results in the efficient formation of exo-2-(cyanomethyl)bicycloheptane.Investigation of the scope of this reaction established that (a) copper(I or II) salts are not effective, (b) propionitrile and methanol give analogous norbornene-solvent adducts, and (c) acetonitrile addition is observed for several cyclic and acyclic olefins.Investigation of the mechanism of solvent addition indicates that the reaction is initiated by photoinduced electron transfer to silver(I) from coordinated norbornene.Reaction of the resulting norbonene cation radical with acetonitrile yields norbornyl cation and cyanomethyl radical.Free-radical chain addition of the cyanomethyl radical to norbornene then leads to product formation.In ethereal solvents, metal ion catalyzed photodimerization of norbornene has previously been reported for copper(I) salts.This reaction can also be effected by copper(II) and silver(I) salts, but not by Tl(I) salts.
