- Understanding the role played by protic ionic liquids (PILs) and the substituent effect for enhancing the generation of: Z-cinnamic acid derivatives
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Photoisomerization of a series of substituted E-cinnamic acids in MeCN in their acid forms and as their corresponding protic ionic liquids (PILs) with light of 300 nm is studied. The nature, strength, number, and position effects of substituents on the photochemical behavior of E-cinnamic derivatives are investigated. The photosensitization of the reaction in the presence of Michler's ketone is also studied at 366 nm and it demonstrates that the triplet-excited state is involved in the reaction. As the presence of n-butylamine needed to form the PILs significantly increases the photoproduct yields in all cases, the role of the PILs is also discussed. Thus, understanding of these fundamental aspects has allowed us to establish an excellent and practical synthetic protocol for successfully synthesizing Z-cinnamic acids. This journal is
- Rodríguez, Roció B.,Rodríguez, Roció B.,Zapata, Ramiro L.,Salum, Mariá L.,Salum, Mariá L.,Erra-Balsells, Rosa,Erra-Balsells, Rosa
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p. 819 - 830
(2020/07/03)
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- Using non-covalent interactions to direct regioselective 2+2 photocycloaddition within a macrocyclic cavitand
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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.
- Nguyen, Nga,Clements, Aspen Rae,Pattabiraman, Mahesh
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p. 2433 - 2443
(2016/03/19)
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- Substituent effects of cis-cinnamic acid analogues as plant growh inhibitors
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1-O-cis-Cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals that has been isolated from Spiraea thunbergii Sieb by Hiradate et al. It derives its strong inhibitory activity from cis-cinnamic acid (cis-CA), which is crucial for phytotoxicity. By preparing and assaying a series of cis-CA analogues, it was previously found that the key features of cis-CA for lettuce root growth inhibition are a phenyl ring, cis-configuration of the alkene moiety, and carboxylic acid. On the basis of a structure-activity relationship study, the substituent effects on the aromatic ring of cis-CA were examined by systematic synthesis and the lettuce root growth inhibition assay of a series of cis-CA analogues having substituents on the aromatic ring. While ortho- and para-substituted analogues exhibited low potency in most cases, meta-substitution was not critical for potency, and analogues having a hydrophobic and sterically small substituent were more likely to be potent. Finally, several cis-CA analogues were found to be more potent root growth inhibitors than cis-CA.
- Nishikawa, Keisuke,Fukuda, Hiroshi,Abe, Masato,Nakanishi, Kazunari,Taniguchi, Tomoya,Nomura, Takashi,Yamaguchi, Chihiro,Hiradate, Syuntaro,Fujii, Yoshiharu,Okuda, Katsuhiro,Shindo, Mitsuru
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p. 132 - 147
(2014/01/06)
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- Templating photodimerization of trans-cinnamic acids with cucurbit[8]uril and γ-cyclodextrin
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(Chemical Equation Presented) Cucurbit[8]uril and γ-cyclodextrin are able to align two olefin molecules in a head-head fashion within their large cavities. Excitation of such templated olefins results in syn head-head cyclobutanes in nearly quantitative yields. The methodology revealed here works with trans-cinnamic acids that do not dimerize either in solution or in the solid state and with the ones that yield only anti head-tail dimer in the solid state.
- Pattabiraman, Mahesh,Natarajan, Arunkumar,Kaanumalle, Lakshmi S.,Ramamurthy
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p. 529 - 532
(2007/10/03)
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