- Energy-Transfer-Mediated Photocatalysis by a Bioinspired Organic Perylenephotosensitizer HiBRCP
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Energy transfer plays a special role in photocatalysis by utilizing the potential energy of the excited state through indirect excitation, in which a photosensitizer determines the thermodynamic feasibility of the reaction. Bioinspired by the energy-transfer ability of natural product cercosporin, here we developed a green and highly efficient organic photosensitizer HiBRCP (hexaisobutyryl reduced cercosporin) through structural modification of cercosporin. After structural manipulation, its triplet energy was greatly improved, and then, it could markedly promote the efficient geometrical isomerization of alkenes from the E-isomer to the Z-isomer. Moreover, it was also effective for energy-transfer-mediated organometallic catalysis, which allowed realization of the cross-coupling of aryl bromides and carboxylic acids through efficient energy transfer from HiBRCP to nickel complexes. Thus, the study on the relationship between structural manipulation and their photophysical properties provided guidance for further modification of cercosporin, which could be applied to more meaningful and challenging energy-transfer reactions.
- Zhang, Yan,Xia, Mingze,Li, Min,Ping, Qian,Yuan, Zhenbo,Liu, Xuanzhong,Yin, Huimin,Huang, Shuping,Rao, Yijian
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p. 15284 - 15297
(2021/11/01)
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- Manganese Catalyzed Enantioselective Epoxidation of α,β-Unsaturated Amides with H2O2
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Herewith, we report the enantioselective epoxidation of electron-deficient cis- and trans-α,β-unsaturated amides with the environmentally benign oxidant H2O2. The catalysts - manganese complexes with bis-amino-bis-pyridine and structurally related ligands - exhibit reasonably high efficiency (up to 100 TON) and excellent chemo- and enantioselectivity (up to 100% and 99% ee, respectively). Crucially, the cis-enamides epoxidation enantioselectivity and yield are dramatically enhanced by the presence of NH-moiety, which effect can be explained by the hydrogen bonding interaction between the cis-enamide substrate and the manganese based oxygen transferring species. (Figure presented.).
- Ottenbacher, Roman V.,Kurganskiy, Vladimir I.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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supporting information
p. 2778 - 2782
(2021/04/29)
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- Contra-thermodynamic E → Z isomerization of cinnamamides via selective energy transfer catalysis
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A bio-inspired, photocatalytic E → Z isomerization of cinnamides is reported using inexpensive (?)-riboflavin (vitamin B2) under irradiation at λ = 402 nm. This operationally simple transformation is compatible with a range of amide derivatives including –NR2, –NHSO2R and N(Boc)2 (up to 99:1 Z:E). Selective energy transfer from the excited state photocatalyst to the starting E-isomer ensures that directionality is achieved: The analogous process with the Z-isomer is inefficient due to developing allylic strain causing chromophore deconjugation. This is supported by X-ray analysis and Stern-Volmer photo-quenching studies. Preliminary validation of the method in manipulating the conformation of a simple model Leu-enkephalin penta-peptide is disclosed via the incorporation of a cinnamamide-based amino acid.
- Becker, Marc R.,Morack, Tobias,Robertson, Jack,Metternich, Jan B.,Mück-Lichtenfeld, Christian,Daniliuc, Constantin,Burley, Glenn A.,Gilmour, Ryan
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- Photocatalyst-free visible light promoted: E → Z isomerization of alkenes
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A simple and green method of visible light driven photocatalytic E to Z isomerization of alkenes has been developed. A variety of (Z)-alkenes can be prepared in the presence of visible light, without any additional photocatalyst. This protocol features photocatalyst-free conditions, which are mild, tolerant, and operationally simple, and is easy to implement.
- Xu, Jianbin,Liu, Na,Lv, Haiping,He, Chixian,Liu, Zining,Shen, Xianfu,Cheng, Feixiang,Fan, Baomin
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supporting information
p. 2739 - 2743
(2020/06/17)
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- Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes
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Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.
- Zhao, Chuan-Qi,Chen, Yue-Gang,Qiu, Hui,Wei, Lei,Fang, Ping,Mei, Tian-Sheng
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supporting information
p. 1412 - 1416
(2019/03/07)
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- Photocatalytic E → Z isomerization of polarized alkenes inspired by the visual cycle: Mechanistic dichotomy and origin of selectivity
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Iteratively executed with exquisite spatial and temporal control, the selective isomerization of polarized alkenes underpins a plethora of complex biological processes ranging from natural product biosynthesis through to the mammalian visual cycle. However, nature's proficiency conceals the inherent difficulties in replicating this contrathermodynamic transformation in the laboratory. Recently, we disclosed the first highly Z-selective isomerization of polarized alkenes, employing the cinnamoyl chromophore as a retinal surrogate under UV-irradiation (402 nm) with (-)-riboflavin (Vitamin B2) as an inexpensive, organic photocatalyst (J. Am. Chem. Soc. 2015, 137, 11254-11257). This study was inspired by the propensity of crystalline (-)-riboflavin in the eyes of vertebrates to invert the intrinsic directionality of retinal isomerization. Herein, we extend this methodology to include a bioinspired, catalytic E → Z isomerization of α,β-unsaturated nitriles, thereby mimicking the intermediate Opsin-derived, protonated Schiff base in the visual cycle with simple polarized alkenes. Replacement of the iminium motif by a cyano group is well tolerated and gives an additional degree of versatility for postisomerization functionalization. Broad substrate scope is demonstrated (up to 99:1 Z:E) together with evidence of mechanistic dichotomy via both singlet and triplet energy transfer mechanisms. Kinetic studies, temperature dependent photostationary state correlations and investigation of substituent-based electronic perturbation of the alkene identified polarization combined with increased Z-isomer activation barriers as the selectivity governing factors in catalysis. This investigation demonstrates the importance of internal structural preorganization on photostationary composition and explicates the augmented Z-selectivity upon hydrogen-alkyl exchange at the β-position of the alkene.
- Metternich, Jan B.,Artiukhin, Denis G.,Holland, Mareike C.,Von Bremen-Kuhne, Maximilian,Neugebauer, Johannes,Gilmour, Ryan
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p. 9955 - 9977
(2018/05/31)
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- Palladium chloride catalyzed photochemical Heck reaction
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PdCl2 catalyzed carbon-carbon bond formation (Heck reaction) between substituted aryl halides and olefins was carried out without a ligand, under irradiation with UV-visible light. The results demonstrated that UV-visible light accelerated the rate of the reaction, leading to an excellent yield of corresponding products. The recovered palladium nanoparticles could be thermally recycled several times. PdCl2 gave excellent conversion up to the fifth addition of substrate.
- Waghmode, Suresh B.,Arbuj, Sudhir S.,Wani, Bina N.,Gopinath
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supporting information
p. 348 - 351
(2013/06/04)
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- Key structural features of cis-cinnamic acid as an allelochemical
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1-O-cis-cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals isolated from Spiraea thunbergii Sieb. It is suggested that it derives its strong inhibitory activity from cis-cinnamic acid, which is crucial for phytotoxicity. It was synthesized to confirm its structure and bioactivity, and also a series of cis-cinnamic acid analogues were prepared to elucidate the key features of cis-cinnamic acid for lettuce root growth inhibition. The cis-cyclopropyl analogue showed potent inhibitory activity while the saturated and alkyne analogues proved to be inactive, demonstrating the importance of the cis-double bond. Moreover, the aromatic ring could not be replaced with a saturated ring. However, the 1,3-dienylcyclohexene analogue showed strong activity. These results suggest that the geometry of the C-C double bond between the carboxyl group and the aromatic ring is essential for potent inhibitory activity. In addition, using several light sources, the photostability of the cinnamic acid derivatives and the role of the C-C double bond were also investigated.
- Abe, Masato,Nishikawa, Keisuke,Okuda, Katsuhiro,Shindo, Mitsuru,Fukuda, Hiroshi,Nakanishi, Kazunari,Tazawa, Yuta,Taniguchi, Tomoya,Park, So-Young,Hiradate, Syuntaro,Fujii, Yoshiharu
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p. 56 - 67,12
(2012/12/12)
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- Sunlight promoted palladium catalysed Mizoroki-Heck, Suzuki-Miyaura and Sonogashira reactions
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The palladium catalysed Mizoroki-Heck, Suzuki-Miyaura and Sonogashira reactions were successfully carried out under irradiation with sunlight. The Heck reaction gives considerable amount of Z product due to photochemical isomerization of initially formed E alkenes. Reaction of methyl 2-iodobenzoate with acrylamide under solar condition furnished 2H-2-benzazepine-1,3-dione rather than the expected derivative of cinnamate while the same reaction with ethyl 2-iodobenzoate gave the desired cinnamide.
- Chaudhary, Anju R.,Bedekar, Ashutosh V.
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p. 6100 - 6103,4
(2020/08/20)
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- Zinc-mediated facile synthesis of α,β-unsaturated primary amides
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A general method for the synthesis of α,β-unsaturated primary amides was achieved by an one-pot, triphenylphosphine-and zinc powder-promoted Wittig reaction of bromoacetamide and aldehydes under solvent-free conditions.
- Feng, Sunlin,Zhang, Zhiying,Jiang, Shilei,Yu, Xiaochun
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experimental part
p. 382 - 384
(2010/11/03)
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- Highly Z-selective synthesis of disubstituted α, β-unsaturated cyanides and amides using 10-P-5 wittig type reagents
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Phosphoranes (10-P-5) bearing cyanomethyl, acetamide, and N, N-dimethylacetamide groups were examined for Wittig type reactions. All three reacted to give the corresponding olefins. The reaction of the cyanomethyl reagent with aldehydes gave α, β-unsatura
- Kojima, Satoshi,Kawaguchi, Kazuhiro,Matsukawa, Shiro,Uchida, Keiichiro,Akiba, Kin-ya
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p. 170 - 171
(2007/10/03)
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- A novel [2 + 2] photodimerization of N-[(E)-3,4-methylenedioxycinnamoyl]dopamine in the solid state.
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[reaction: see text] To give photoreactivity to catecholamines, N-cinnamoyl-substituted dopamines (E)-5a-5c and O,O'-dimethyldopamines (E)-3a-3c were prepared under solvent-free conditions. A particularly interesting observed photoreactivity was that of N-[(E)-3,4-methylenedioxycinnamoyl]dopamine ((E)-5c), which underwent a novel type of [2 + 2] photodimerization in the solid state, giving exclusively a tricyclic product 8. This reaction is the first example of solid-state photoaddition of an alkene to the benzene ring.
- Ito,Horie,Shindo
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p. 2411 - 2413
(2007/10/03)
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- Compelled orientational control of the solid-state photodimerization of trans-cinnamamides: Dicarboxylic acid as a non-covalent linker
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The 2:1 hydrogen-bonded cocrystals 1a·ox, la·su, 1a·pht, 1a·fu, 1b·ox, 1c·ox, 1d·ox between trans-cinnamamides (1a-1d) and dicarboxylic acids (ox, su, gl, fu, pht) were prepared and characterized by IR and powder X-ray techniques. The crystal structures of 1a·pht, 1a·ox and 1a·fu were solved by single crystal X-ray diffraction. Phthalic acid (pht) caused β-type photodimerization of trans-cinnamamide (1a) in the cocrystal and functioned as a non-covalent linker like gauche 1,2-diamines in photodimerization of trans-cinnamic acids. Oxalic acid (ox) enforced 1a to take a bilayer structure that is suitable for β-type photodimerization. In the case of fumaric acid (fu), cross photodimerization with 1a occurred to give a cycloadduct 4. For the cocrystals 1a·pht and 1a·fu, pedal-like motion was assumed to occur prior to the dimerization. (C) 2000 Elsevier Science Ltd.
- Ito, Yoshikatsu,Hosomi, Hiroyuki,Ohba, Shigeru
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p. 6833 - 6844
(2007/10/03)
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- Structure and Photoisomerization of (E)- and (Z)-Cinnamamides and Their Lewis Acid Complexes
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The spectroscopic properties and photoisomerization reactions of several (E)- and (Z)-cinnamamides have been investigated in the absence and presence of the strong Lewis acid BF3.The (E)-cinnamamides are essentially planar and exist predominantly in the enone s-cis conformation, except in the case of the α-methyl tertiary amide which adopts the s-trans conformation in order to minimize nonbonded repulsion.The (Z)-cinnamamides exist predominantly in the highly nonplanar s-trans conformation.This unusual conformational preference is attributed to intramolecular charge transfer from the aromatic to amide functionality.Photoisomerization efficiencies are dependent upon N-alkylation, aromatic substitution, α-alkylation, and excitation wavelength.These effects are attributed to the existence of two lowest energy ?,?* singlet states (one reactive and one nonreactive) whose relative energies are dependent upon substitution.The cinnamamides form 1:1 complexes with BF3 with equilibrium constants >103.Complexation alters both the electronic structure and photochemical behavior of the cinnamamides.Quantitative E -> Z isomerization has been observed for the BF3 complexes of two tertiary amides.
- Lewis, Frederick D.,Elbert, Jeffrey E.,Upthagrove, Alana L.,Hale, Paul D.
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p. 553 - 561
(2007/10/02)
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