56586-34-6Relevant academic research and scientific papers
Using non-covalent interactions to direct regioselective 2+2 photocycloaddition within a macrocyclic cavitand
Nguyen, Nga,Clements, Aspen Rae,Pattabiraman, Mahesh
, p. 2433 - 2443 (2016/03/19)
The relative orientation of guests within ternary inclusion complexes is governed by the host-guest and guest-guest supramolecular interactions. Selectivity in 2+2 photocycloaddition between two alkenes included within a macrocyclic cavitand (γ-cyclodextrin) can be controlled using non-covalent interactions. In this manuscript, we report cavitand-mediated control of regioselectivity between alkyl cinnamates using non-covalent interactions. Using this method, we have shown that regioselectivity can be switched completely from a head-to-head dimer to a head-to-tail dimer. The reactions were also stereoselective in most cases. Stoichiometry experiments were performed to explore relative stabilities of the complexes, which indicate that the ternary complex is more stable than others. Selectivity in the photocycloaddition reaction was also applied retrospectively to deduce intermolecular orientations. Time-dependent conversion study we performed indicates that the observed reactivity of alkenes is representative of the intermolecular orientations in the bulk of the complex medium. Experimental observations and computational studies were used to qualitatively understand the complex structures, and relative magnitudes of the weak interactions. The reactions of complexes were studied in slurry form, and the extent of reaction control suggests a solid-state-like behavior.
Transient states in [2 + 2] photodimerization of cinnamic acid: Correlation of solid-state NMR and X-ray analysis
Khan, Mujeeb,Brunklaus, Gunther,Enkelmann, Volker,Spiess, Hans-Wolfgang
, p. 1741 - 1748 (2008/09/18)
13C-CPMAS and other solid-state NMR methods have been applied to monitor the solid-state reactions of trans-cinnamic acid derivatives, which are the pioneer and model compounds in the field of topochemistry previously studied by X-ray diffracti
Templating photodimerization of trans-cinnamic acid esters with a water-soluble Pd nanocage
Karthikeyan,Ramamurthy
, p. 452 - 458 (2007/10/03)
A water-soluble octahedral Pd nanocage acting as a reaction vessel templates the photodimerization of substituted trans-cinnamic acid methyl esters in water. Irradiation of the host-guest complexes of trans-cinnamic acid methyl esters with the Pd nanocage resulted in selective formation of a syn head-head dimer in addition to the corresponding cis isomer. These results suggest that the guest molecules are preoriented in a selective fashion with the hydrophilic ester group facing water and the hydrophobic aryl group tucked within the cavity of the host. Such an orientation occurs at the hydrophobic-hydrophilic interface between the nanocage exterior and interior. Weak intermolecular C-H-π and π-π interactions between the host and the guest(s) are likely to be responsible for the lack of mobility of the reactant olefins during their short excited-state lifetime.
Controlled photocycloaddition of unsaturated carboxylates intercalated in hydrotalcite clay interlayers
Takagi, Katsuhiko,Shichi, Tetsuya,Usami, Hisanao,Sawaki, Yasuhiko
, p. 4339 - 4344 (2007/10/02)
Photochemical cycloaddition for several unsaturated carboxylates has been studied in the presence of hydrotalcite clays. Syn head-to-head cyclodimers were selectively formed in the irradiation of sodium cinnamates intercalated in the dispersed clays. On the other hand, two isomers of syn head-to-head and syn head-to-tail cyclodimers were formed for the case of (phenylethenyl)benzoates. The degree of intercalation was shown to be dependent on the structures of the carboxylates. X-ray diffraction analyses revealed that the carboxylates are intercalated as a monolayer, which suggests an alternate anti-parallel packing since a clay interlayer possesses two ionic surfaces, top and bottom. The product selectivity was shown to be controlled by the relative distances of double bonds from the ionic surfaces of the clay. The molecular aggregates of intercalated carboxylates were affected by adding photoinactive coadsorbates; the major photochemical processes shifted from photocycloadditions to cis-trans isomerizations and from excimer to monomer fluorescence emissions.
Lewis Acid Catalysis of Photochemical Reactions. 7. Photodimerization and Cross-Cycloaddition of Cinnamic Esters
Lewis, Frederick D.,Quillen, Suzanne L.,Hale, Paul D.,Oxman, Joe D
, p. 1261 - 1267 (2007/10/02)
The effects of Lewis acid complexation upon the molecular structure, solid-state photodimerization, and solution dimerization and cross-cycloaddition of cinnamic esters have been investigated.Comparison of crystal structures for free and SnCl4-complexed ethyl cinnamate indicates that the enone double bonds are lengthened, the single bonds are shortened, and the enone conformation changes from s-cis to s-trans upon complexation.These changes are consistent with calculated changes in ? bonding and net charges.Solid-state photodimerization of free and complexed cinnamic esters and related molecules yield syn head-to-tail (α-truxillate) dimers.In most cases the Lewis acid complexes dimerize more efficiently and stereoselectively than the free esters.Photodimerization and cross-cycloaddition of methyl cinnamate in dilute solution is also catalyzed by Lewis acids.The mechanism of these reactions involves electronic excitation of a ground-state methyl cinnamate-Lewis acid complex followed by reaction of the excited complex with ground-state ester (dimerization) or simple olefin (cross-cycloaddition).The catalytic effect of Lewis acids is attributed to an increase in excited-state lifetime and reactivity.
PREPARATION OF CHLORO-α-TRUXILLIC ACIDS VIA 3-METHYL-4-NITRO-5-STYRYLISOXAZOLE PHOTODIMERS
Baracchi, Antonella,Chimichi, Stefano,Sio, Francesco De,Donati, Donato,Nesi, Rodolfo,et al.
, p. 2863 - 2870 (2007/10/02)
Chloro-α-truxillic acids (3b-e) were prepared by oxidation of the photodimers (2b-e) of 3-methyl-4-nitro-5-chlorostyrylisoxazoles (1b-e).
Pulse Radiolysis and 77 K Matrix γ Irradiation of Dimethyl Truxinates and trans-Methyl Cinnamate in 2-Methyltetrahydrofuran
Takamuku, Setsuo,Kigawa, Hitoshi,Suematsu, Hiroyuki,Toki, Susumu,Tsumori, Kunihiko,Sakurai, Hiroshi
, p. 1861 - 1865 (2007/10/02)
One-electron reduction of dimethyl μ-truxinate (μ-DMT), dimethyl β-truxinate (β-DMT), and dimethyl α-truxillate (α-DMT) has been investigated by pulse radiolysis and 77 K matrix γ irradiation of the 2-methyltetrahydrofuran solutions.Cycloreversion of the radical anions formed by an electron attachment to these cyclobutanes was observed in all cases, even at 77 K.The orientation of the cycloreversion was dependent on the stereochemistry of the cyclobutanes, and the selectivity was reasonably explained by a so-called cis effect; the best possible release of steric hindrance decides the primary step of the reaction.In 77 K matrix γ irradiation of α-DMT, an intense IR absorption was found after the photobleaching of trapped electrons with light >690 nm.In other DMTs, the IR absorption band was not observed while the cycloreversion of DMT by mobile electrons occurred.Thus, the IR band in the case of α-DMT was assigned to an associated dimer anion due to the interaction between the radical anion and the neutral molecule pair of trans-methyl cinnamate originally formed by the cycloreversion of α-DMT.The dimer anion was presumed to be oriented in a head-to-tail structure in a solvent cage on the basis of the original configuration of α-DMT.
Solid-State Photooligomerization of an Extended Chiral Bifunctional Monomer, (+)-2,4:3,5-Di-O-methylene-D-mannitol 1,6-Di-trans-cinnamate
Bernstein, Joel,Green, Bernard S.,Rejtoe, Miriam
, p. 323 - 328 (2007/10/02)
Irradiation of crystalline (+)-2,4:3,5-di-O-methylene-D-mannitol 1,6-di-trans-cinnamate (1) induces intermolecular cyclobutane formation leading to chiral oligomers of increasing length.The dimer, trimer, tetramer, and pentamer have been isolated and characterized.The intramolecular distance between the olefinic residues within the molecules of 1 is larger than in any previous examples of solid-state photodimerization or oligomerization and, in spite of the large, bulky tetraoxa-cis-decalin group separating the reaction centers, the cinnamate groups of the monomer are properly aligned for intermolecular photocycloaddition.Crystals of 1 are monoclinic, a = 15.218(6) Angstroem, b = 13.217(7) Angstroem, c = 5.882(3) Angstroem, β = 76.95(3) deg; the space group is P21, with two molecules in the cell.The structure has been solved by direct methods and refined to an R factor of 0.043 on 2270 nonzero reflections.The crystal structure analysis establishes the correct molecular structure of the sugar alcohol derivative, previously in doubt, and elucidates the molecular packing which is responsible for the observed prodicts.The chemical consequences of solid-state irradiation of compound 12, a monothiophene analogue of 1, have been considered; 12, however, shows an unexpected reluctance to crystallize in the same structure as 1.
