The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Patrick S Mariano - One of the best experts on this subject based on the ideXlab platform.
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direct and indirect single electron transfer set photochemical approaches for the preparation of novel Phthalimide and naPhthalimide based lariat type crown ethers
Beilstein Journal of Organic Chemistry, 2014Co-Authors: Patrick S Mariano, Ung Chan YoonAbstract:In this review, we describe direct and indirect photochemical approaches that have been developed for the preparation of Phthalimide- and naPhthalimide-based, lariat-type crown ethers. The direct route utilizes a strategy in which nitrogen-linked side chains containing polyethoxy-tethered Phthalimides and naPhthalimides, possessing terminal α-trialkylsilyl groups, are synthesized utilizing concise routes and UV-irradiation to form macrocyclic ring systems. In contrast, the indirect route developed for the synthesis of lariat-type crown ethers employs sequences in which SET-promoted macrocyclization reactions of α-trialkylsilyl-terminated, polyethoxy-tethered Phthalimides and naPhthalimides are followed by a side chain introduction through substitution reactions at the amidol centers in the macrocyclic ethers. The combined observations made in these investigations demonstrate the unique features of SET-promoted photocyclization reactions that make them well-suited for the use in the synthesis of functionalized crown ethers. In addition, while some limitations exist for the general use of SET-photochemical reactions in large-scale organic synthesis, important characteristics of the photoinduced macrocyclization reactions make them applicable to unique situations in which high temporal and spatial control is required.
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A strategy for the preparation of cyclic polyarenes based on single electron transfer-promoted photocyclization reactions
Research on Chemical Intermediates, 2012Co-Authors: Hea Jung Park, Ung Chan Yoon, Jung Hei Choi, Byeol Na Park, Patrick S MarianoAbstract:Single electron transfer (SET)-promoted photocyclization reactions of substrates comprised of benzylsilane tethered to Phthalimides were subjected to an exploratory study in order to probe a new approach for the preparation of cyclic polyarenes. The results show that UV irradiation of the substrates leads to efficient photochemical reactions that are initiated by SET from benzylsilane moieties to the excited Phthalimide acceptor. Ensuing desilylation reactions of the benzylsilane cation radical moieties in the intermediate zwitterionic biradicals and proton transfer gives biradical precursors of the cyclic polyarene products. The observations made in this effort suggests that SET photochemical methods, which have been employed earlier to generate cyclic poly-ethers, -thioethers and -amides, serve as a useful method to access potentially interesting macrocyclic targets.
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the synthetic potential of Phthalimide set photochemistry
Accounts of Chemical Research, 2001Co-Authors: Ung Chan Yoon, Patrick S MarianoAbstract:The authors' studies in the area of Phthalimide photochemistry are discussed in the context of the development of new methods for N-heterocycle synthesis. Emphasis is given to reactions which are initiated by both intermolecular and intramolecular SET from silicon-containing electron donors to excited states of Phthalimides and related maleimides and conjugated imides. The photoaddition and photocyclization processes which ensue follow mechanistic pathways, in which efficient desilylation of initially formed radical cation occurs to generate radical pair and biradical intermediates that serve as precursors of the products. Several examples that demonstrate the preparative potential of these reactions are presented. These are taken from the authors' investigations of (1) phthalimido-alkylsilane photocyclization reactions, (2) azomethine ylide-forming excited-state processes of N-(trimethylsilylmethyl)Phthalimide, and (3) photoaddition and photocyclization reactions of Phthalimide α-silyl ether, thioether, ...
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Exploratory Study of Photocyclization Reactions of N-(Trimethylsilylmethylthioalkyl)Phthalimides
Bulletin of The Korean Chemical Society, 1994Co-Authors: Ung Chan Yoon, Patrick S MarianoAbstract:Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethylthioalkyl)Phthalimides (alkyl=ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl). Photocyclizations occur in methanol in modest to high yields to produce cyclized products in which Phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from sulfur in the -silylmethylthioalkyl groups to the singlet excited state Phthalimide moieties followed by desilylation of the intermediate -silylmethylthio cation radicals and cyclization by radical coupling is proposed. In contrast, photoreactions of N-(trimethylsilylmethylthioalkyl)Phthalimides in acetone follow different reaction routes to produce another cyclized products in which carbon-carbon bond formation takes place between the Phthalimide carbonyl carbon and the carbon to silicon and sulfur atoms via triplet carbonyl hydrogen abstraction pathway. The normal singlet SET pathway dominates this triplet process for photoreactions of these substances in methanol while the triplet process dominates the singlet SET pathway for those in acetone. The efficient and regioselective cyclization reactions observed for photolyses in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.
Ung Chan Yoon - One of the best experts on this subject based on the ideXlab platform.
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direct and indirect single electron transfer set photochemical approaches for the preparation of novel Phthalimide and naPhthalimide based lariat type crown ethers
Beilstein Journal of Organic Chemistry, 2014Co-Authors: Patrick S Mariano, Ung Chan YoonAbstract:In this review, we describe direct and indirect photochemical approaches that have been developed for the preparation of Phthalimide- and naPhthalimide-based, lariat-type crown ethers. The direct route utilizes a strategy in which nitrogen-linked side chains containing polyethoxy-tethered Phthalimides and naPhthalimides, possessing terminal α-trialkylsilyl groups, are synthesized utilizing concise routes and UV-irradiation to form macrocyclic ring systems. In contrast, the indirect route developed for the synthesis of lariat-type crown ethers employs sequences in which SET-promoted macrocyclization reactions of α-trialkylsilyl-terminated, polyethoxy-tethered Phthalimides and naPhthalimides are followed by a side chain introduction through substitution reactions at the amidol centers in the macrocyclic ethers. The combined observations made in these investigations demonstrate the unique features of SET-promoted photocyclization reactions that make them well-suited for the use in the synthesis of functionalized crown ethers. In addition, while some limitations exist for the general use of SET-photochemical reactions in large-scale organic synthesis, important characteristics of the photoinduced macrocyclization reactions make them applicable to unique situations in which high temporal and spatial control is required.
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A strategy for the preparation of cyclic polyarenes based on single electron transfer-promoted photocyclization reactions
Research on Chemical Intermediates, 2012Co-Authors: Hea Jung Park, Ung Chan Yoon, Jung Hei Choi, Byeol Na Park, Patrick S MarianoAbstract:Single electron transfer (SET)-promoted photocyclization reactions of substrates comprised of benzylsilane tethered to Phthalimides were subjected to an exploratory study in order to probe a new approach for the preparation of cyclic polyarenes. The results show that UV irradiation of the substrates leads to efficient photochemical reactions that are initiated by SET from benzylsilane moieties to the excited Phthalimide acceptor. Ensuing desilylation reactions of the benzylsilane cation radical moieties in the intermediate zwitterionic biradicals and proton transfer gives biradical precursors of the cyclic polyarene products. The observations made in this effort suggests that SET photochemical methods, which have been employed earlier to generate cyclic poly-ethers, -thioethers and -amides, serve as a useful method to access potentially interesting macrocyclic targets.
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the synthetic potential of Phthalimide set photochemistry
Accounts of Chemical Research, 2001Co-Authors: Ung Chan Yoon, Patrick S MarianoAbstract:The authors' studies in the area of Phthalimide photochemistry are discussed in the context of the development of new methods for N-heterocycle synthesis. Emphasis is given to reactions which are initiated by both intermolecular and intramolecular SET from silicon-containing electron donors to excited states of Phthalimides and related maleimides and conjugated imides. The photoaddition and photocyclization processes which ensue follow mechanistic pathways, in which efficient desilylation of initially formed radical cation occurs to generate radical pair and biradical intermediates that serve as precursors of the products. Several examples that demonstrate the preparative potential of these reactions are presented. These are taken from the authors' investigations of (1) phthalimido-alkylsilane photocyclization reactions, (2) azomethine ylide-forming excited-state processes of N-(trimethylsilylmethyl)Phthalimide, and (3) photoaddition and photocyclization reactions of Phthalimide α-silyl ether, thioether, ...
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Exploratory Study of Photocyclization Reactions of N-(Trimethylsilylmethylthioalkyl)Phthalimides
Bulletin of The Korean Chemical Society, 1994Co-Authors: Ung Chan Yoon, Patrick S MarianoAbstract:Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethylthioalkyl)Phthalimides (alkyl=ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl). Photocyclizations occur in methanol in modest to high yields to produce cyclized products in which Phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from sulfur in the -silylmethylthioalkyl groups to the singlet excited state Phthalimide moieties followed by desilylation of the intermediate -silylmethylthio cation radicals and cyclization by radical coupling is proposed. In contrast, photoreactions of N-(trimethylsilylmethylthioalkyl)Phthalimides in acetone follow different reaction routes to produce another cyclized products in which carbon-carbon bond formation takes place between the Phthalimide carbonyl carbon and the carbon to silicon and sulfur atoms via triplet carbonyl hydrogen abstraction pathway. The normal singlet SET pathway dominates this triplet process for photoreactions of these substances in methanol while the triplet process dominates the singlet SET pathway for those in acetone. The efficient and regioselective cyclization reactions observed for photolyses in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.
Axel G. Griesbeck - One of the best experts on this subject based on the ideXlab platform.
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Photochemistry of Phthalimides: decarboxylation, addition, macrocyclization and deprotection
ChemInform, 2020Co-Authors: Michael Oelgemöller, Axel G. GriesbeckAbstract:A large number of useful photochemical transformations in the Phthalimide series were developed. These processes allow the photochemical synthesis of interesting new compounds via addition, ring expansion, cyclization or fragmentation reactions. Beside the spacer fragments shown in here also peptide or olefinic linkers were examined, and next to Phthalimides other imides like quinolinic- and trimellitic acid imides were suitable chromophores for PET-reactions.
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Photoinduced electron transfer reactions of Phthalimides
2020Co-Authors: Anna Bartoschek, Axel G. Griesbeck, Michael OelgemoellerAbstract:The influence of deactivation processes (like hydrogen bonding) on the photodecarboxylation of w-phthalimido potassium carboxylates was studied using a series of N-phthaloyl dipeptides. Furthermore, the decarboxylative addition of unfunctionalized carboxylates and heteroatom-functionalized carboxylates to Phthalimides was developed as a highly chemoselective radical addition reaction.
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N-(2-Phenethyl)Phthalimide
Acta Crystallographica Section E-structure Reports Online, 2006Co-Authors: Klausdieter Warzecha, Jörg M. Neudörfl, Axel G. GriesbeckAbstract:The molecule of the title compound, C16H13NO2, contains two planar units, viz. a Phthalimide system and a phenyl ring in almost parallel orientation, linked by an ethylene bridge. In the crystal structure, the molecules form centrosymmetric pairs which are held together by π–π interactions between the Phthalimide systems. The latter are stacked in a head-to-tail fashion with an interplanar distance of 3.263 (6) A.
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photoinduced decarboxylative benzylation of Phthalimide triplets with phenyl acetates a mechanistic study
Journal of Physical Chemistry A, 2006Co-Authors: Klausdieter Warzecha, Helmut Gorner, Axel G. GriesbeckAbstract:The photodecarboxylative benzylation of N-alkyl, N-arylalkyl, and N-aryl Phthalimides with arylacetic acids in aqueous solution proceeds via electron transfer from the arylalkanoate to the excited triplet state of the Phthalimide, either formed directly or upon sensitization with acetone. The rate constant for triplet quenching of N-methylPhthalimide is kq < 107 M-1 s-1 for 2-phenylacetic acid and kq = (1−3) × 109 M-1 s-1 for its mono-, di- and trimethoxy-substituted derivatives, suggesting a change of the mechanism for the primary oxidation step from a Photo-Kolbe type reaction yielding an acyloxy radical to a pseudo-Photo-Kolbe process involving the formation of resonance-stabilized zwitterion radicals as intermediates.
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Photoinduced electron-transfer processes of Phthalimides
ChemInform, 2003Co-Authors: Michael Oelgemöller, Axel G. GriesbeckAbstract:In terms of synthetic applications, the Phthalimide system has attracted much attention over the past three decades, as noticeable by a number of summarizing reviews. Although the photochemistry of Phthalimide derivatives is similar to that of carbonyl compounds, it covers additional reactivity features due to the remarkably high oxidizing power of the excited singlet and triplet states. Thus, the presence of energetically feasible electron donor groups leads to the generation of radical ions that can undergo nonproductive (back) electron transfer, direct radical ion combination, or mesolytic extrusion of a suitable leaving group (e.g., a proton, silyl cation, or carbon dioxide), respectively. The competition between these processes can be controlled by varying the redox potentials, the stability of the radical cations, and the leaving group ability. The photophysical and electrochemical properties of Phthalimides are well documented. In acetonitrile, -alkylPhthalimides show relatively unstructured UV absorption spectra with absorption maxima around 235 nm (π,π*) and 290 nm (π,π*), respectively. In ethanol or acetonitrile at room temperature, they exhibit weak fluorescence with low quantum yields (Φf < 1 × 10−3). In the absence of oxygen in alcohol, N-alkylPhthalimides show broad structureless phosphorescence centered around 450 nm with quantum yields between Φp = 0.4–0.7 and triplet lifetimes of τp = 0.7–1.04 s (at −196°C). N-MethylPhthalimide is reversibly reduced to the corresponding radical anion at ca. −1.35 V in DMF, and at ca. −1.5 V in acetonitrile (vs. SCE),respectively, but the presence of a hydrogen donor site in the side chain has a dramatic effect on the redox properties. Based on the available photophysical and electrochemical data, it is possible to estimate the feasibility of a photoinduced electron transfer (PET)for various Phthalimide/donor pairs. The limiting maximum oxidation potential of the electron donorthus depends on the nature of the electronically excited state of the Phthalimide electron acceptor and can be estimated from the Rehm-Weller equation. Thus, if the first excited singlet state is involved (E00= 3.8 eV), the limiting oxidizing power for an isoenergetic electron transfer is ca. 2.4 V (vs. SCE). If the first excited triplet state is involved (E00 = 3.1 eV), the limiting oxidizing power decreases to ca. 1.7 V(vs. SCE). In cases where the spectroscopically nondetectable second triplet state is populated (E00 = 3.6eV), the oxidizing power increases by about 500 mV.
Warinthorn Chavasiri - One of the best experts on this subject based on the ideXlab platform.
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Synthesis ofN-phenylPhthalimide Derivatives as α-Glucosidase Inhibitors
Archives of Pharmacal Research, 2007Co-Authors: Wanchai Pluempanupat, Sirichai Adisakwattana, Sirintorn Yibchok-anun, Warinthorn ChavasiriAbstract:Sixteen N -phenylPhthalimide derivatives were synthesized and their ability to inhibit α-glucosidase was investigated. N -(2,4-dinitrophenyl)Phthalimide was a potent inhibitor of yeast α-glucosidase (IC_50; 0.158 ± 0.005 mM) and maltase (IC_50; 0.051 ± 0.008 mM), whereas it did not inhibit sucrase. From a Lineweaver-Burk plot of α-glucosidase kinetics, N -(2,4-dichlorophenyl) Phthalimide was found to be a competitive inhibitor of yeast α-glucosidase. These results indicate that N -(2,4-dinitrophenyl)Phthalimide could be a representative of a new group of α-glucosidase inhibitors.
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Synthesis of N-phenylPhthalimide derivatives as α-glucosidase inhibitors
Archives of Pharmacal Research, 2007Co-Authors: Wanchai Pluempanupat, Sirichai Adisakwattana, Sirintorn Yibchok-anun, Warinthorn ChavasiriAbstract:Sixteen N-phenylPhthalimide derivatives were synthesized and their ability to inhibit alpha-glucosidase was investigated. N-(2,4-dinitrophenyl)Phthalimide was a potent inhibitor of yeast alpha-glucosidase (IC50; 0.158 +/- 0.005 mM) and maltase (IC50; 0.051 +/- 0.008 mM), whereas it did not inhibit sucrase. From a Lineweaver-Burk plot of alpha-glucosidase kinetics, N-(2,4-dichlorophenyl)Phthalimide was found to be a competitive inhibitor of yeast alpha-glucosidase. These results indicate that N-(2,4-dinitrophenyl)Phthalimide could be a representative of a new group of alpha-glucosidase inhibitors.
Wanchai Pluempanupat - One of the best experts on this subject based on the ideXlab platform.
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Synthesis ofN-phenylPhthalimide Derivatives as α-Glucosidase Inhibitors
Archives of Pharmacal Research, 2007Co-Authors: Wanchai Pluempanupat, Sirichai Adisakwattana, Sirintorn Yibchok-anun, Warinthorn ChavasiriAbstract:Sixteen N -phenylPhthalimide derivatives were synthesized and their ability to inhibit α-glucosidase was investigated. N -(2,4-dinitrophenyl)Phthalimide was a potent inhibitor of yeast α-glucosidase (IC_50; 0.158 ± 0.005 mM) and maltase (IC_50; 0.051 ± 0.008 mM), whereas it did not inhibit sucrase. From a Lineweaver-Burk plot of α-glucosidase kinetics, N -(2,4-dichlorophenyl) Phthalimide was found to be a competitive inhibitor of yeast α-glucosidase. These results indicate that N -(2,4-dinitrophenyl)Phthalimide could be a representative of a new group of α-glucosidase inhibitors.
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Synthesis of N-phenylPhthalimide derivatives as α-glucosidase inhibitors
Archives of Pharmacal Research, 2007Co-Authors: Wanchai Pluempanupat, Sirichai Adisakwattana, Sirintorn Yibchok-anun, Warinthorn ChavasiriAbstract:Sixteen N-phenylPhthalimide derivatives were synthesized and their ability to inhibit alpha-glucosidase was investigated. N-(2,4-dinitrophenyl)Phthalimide was a potent inhibitor of yeast alpha-glucosidase (IC50; 0.158 +/- 0.005 mM) and maltase (IC50; 0.051 +/- 0.008 mM), whereas it did not inhibit sucrase. From a Lineweaver-Burk plot of alpha-glucosidase kinetics, N-(2,4-dichlorophenyl)Phthalimide was found to be a competitive inhibitor of yeast alpha-glucosidase. These results indicate that N-(2,4-dinitrophenyl)Phthalimide could be a representative of a new group of alpha-glucosidase inhibitors.