86970-68-5Relevant academic research and scientific papers
Organic Photochemistry with 6.7-eV Photons. The Divergent Photobehavior of exo- and endo-7-Methyl-2-norcarene
Leigh, William J.,Srinivasan, R.
, p. 3970 - 3979 (2007/10/02)
The photochemistry of exo- and endo-7-methylbicyclohept-2-ene (7-methyl-2-norcarene) upon direct and toluene-sensitized photolysis has been investigated.Direct photolysis of the two isomers in hydrocarbon solution with monochromatic 214-nm light leads to widely divergent photobehavior.Ring opening, yielding cis-5-methyl-1,3,6-heptatriene (via a formal process), and exo-endo isomerization are major decomposition pathways in both cases, accounting for 30-45percent of the observed products.The formation of 7-methylnorbornene and 4-methylbicyclohept-2-ene is observed to proceed stereospecifically in each case, while the formation of cyclopropyl ring opening/hydrogen migration products appears to depend strongly on the orientation of the methyl group in the starting isomer.Common biradical intermediates are thus believed not to be involved in the direct photolyses of 2 and 3.Toluene-sensitized photolysis of the two isomers leads to formation of exo-4-methylbicyclohept-2-ene (the photochemical vinylcyclopropane rearrangement) and exo-endo isomerization.These results are rationalized in terms of the expected behavior of two common biradical intermediates, which are formed with different efficiencies from the isomeric 2 and 3 upon triplet sensitization.
Photochemistry of Alkenes. 6. Direct Irradiation of 1,5-Hexadienes: and Sigmatropic Allyl Shifts
Manning, T. D. R.,Kropp, Paul J.
, p. 889 - 897 (2007/10/02)
The photochemical behavior of a series of alkyl-substituted 1,5-hexadienes has been studied.Competing allylcyclopropane formation and rearrangement to an isomeric 1,5-hexadiene via competing and sigmatropic allyl shifts, respectively, were observed.In one case a product (30 from 27) and in another a product (35 from 31) was obtained, but only in low yield.Extensive cis trans isomerization competed with the allyl shifts, and, in addition, other products were obtained which are characteristic of the photochemical behavior of isolated double bonds.At low conversion diene 10t underwent stereoselective rearrangement to 8t and 11t, whereas the cis isomer 10c afforded mixtures of the cis and trans isomers of 8 and 11.Attempts to induce the allyl migrations by sensitization with p-xylene or by irradiation at 254 nm afforded only cis trans isomerization.It is concluded that the allyl migrations occur via an excited state involving interaction between the double bonds and requiring a conformation in which the central C3-C4 bond is in a plane orthogonal to both double bonds, as proposed previously.In contrast with the acyclic dienes, 1,5-cyclooctadiene (50) afforded products 51-53 from competing , , and allyl shifts, respectively.The divergent behavior in this case apparently arises because appropriate interaction between the two double bonds can occur only in the boat conformation.
