3806-60-8Relevant articles and documents
Enantiodifferentiation in the Photoisomerization of (Z,Z)-1,3-Cyclooctadiene in the Cavity of γ-Cyclodextrin-Curcubit[6]uril-Wheeled [4]Rotaxanes with an Encapsulated Photosensitizer
Yan, Zhiqiang,Huang, Qinfei,Liang, Wenting,Yu, Xingke,Zhou, Dayang,Wu, Wanhua,Chruma, Jason J.,Yang, Cheng
, p. 898 - 901 (2017/02/26)
A biphenyl photosensitizer axle was implanted into the cavities of native and capped γ-cyclodextrins through rotaxanation using a cucubit[6]uril-templated azide-alkyne 1,3-dipolar cycloaddition, resulting in the construction of highly defined chiral binding/sensitizing sites. The orientation and interaction of the axle and capping moieties at the ground and excited states were interrogated by NMR, UV-vis, circular dichroism, and fluorescence spectroscopic studies. In situ photoisomerization of (Z,Z)-1,3-cyclooctadiene sensitized in the cavity of these [4]rotaxanes afforded (Z,E)-1,3-cyclooctadiene in up to 15.3% ee, which represents the highest level of enantiodifferentiation obtained to date for this supramolecular photochirogenesis.
Optically active (E,Z)-1,3-cyclooctadiene: First enantioselective synthesis through asymmetric photosensitization and chiroptical property
Inoue, Yoshihisa,Tsuneishi, Hiroshi,Hakushi, Tadao,Tai, Akira
, p. 472 - 478 (2007/10/03)
Enantiodifferentiating photoisomerizations of (Z,Z)-1,3-cyclooctadiene (1ZZ) to the chiral E,Z-isomer 1EZ were performed at varying temperatures in the presence of some benzenepoly-, naphthalene(di)-, and anthracenecarboxylates. Of these chiral sensitizers, (-)-menthyl benzenehexacarboxylate afforded the highest enantiomeric excesses (ee's) up to 10% and 18% in pentane at 25 and -40°C, respectively. In contrast, the use of polar solvents greatly diminished the product's ee, suggesting intervention of a radical ionic rather than exciplex intermediate in these solvents. Optically pure 1EZ is shown to possess anomalously high specific rotation and circular dichroism as a simple diene chromophore: [α]25(D) 1380°(CH2Cl2), Δε 12.8 M-1 cm-1 (λ(ext) 228 nm, cyclohexane). The chiroptical properties observed not only correct the previous data but also present the conclusive evidence for the recent theoretical predictions.
Cyclobutene photochemistry. Identification of the excited states responsible for the ring-opening and cycloreversion reactions of alkylcyclobutenes
Leigh,Zheng,Nguyen,Werstiuk,Ma
, p. 4993 - 4999 (2007/10/02)
Two substituted bicyclic cyclobutene derivatives - 7-methyl- and 7-(trifluoromethyl)bicyclo[4.2.0]oct-7-ene - have been prepared. Gas- and solution-phase UV absorption and Hel UV photoelectron spectra have been recorded for the two compounds as well as for the parent hydrocarbon bicyclo[4.2.0]oct-7-ene. The gas-phase spectra suggest that the π,R(3s) state is the lowest energy state in bicyclo[4.2.0]octene and the 7-methyl derivative but is raised to higher energies than the π,π* state in the 7-trifluoromethyl derivative. Direct photolysis of the three compounds in hydrocarbon solution with monochromatic far-UV (193 and 214 nm) light leads to competitive ring opening to the corresponding cis,cis- and cis,trans-1,3-cyclooctadiene derivatives, as well as fragmentation to cyclohexene and alkyne in all three cases. Product quantum yields (193-nm excitation) have been measured for both substituted derivatives relative to those for the parent compound. The quantum yields of fragmentation products are highest for the methyl- and unsubstituted compounds, suggesting that these products arise from a Rydberg-like excited state. In contrast, ring opening is most efficient for the trifluoromethyl-substituted compound, although the diene distributions obtained from the reaction do not vary throughout the series. These results indicate that nonstereospecific ring opening arises largely from the π,π* state of cyclobutene. The contribution to the fragmentation process from a concerted [σ2s+σ2s] cycloreversion pathway is minor, at best. The wavelength dependence of the product distributions from photolysis of the three derivatives is in perfect accord with these assignments.
