Photochemistry of N-phthaloyl derivatives of electron-donor-substituted amino acids

Griesbeck, Axel G.; Henz, Andreas; Hirt, J.; Ptatschek, V.; Engel, Thomas; Löffler, Dagmara; Schneider, F. W.

doi:10.1016/s0040-4020(01)80787-0

Cited by 42 publications

(36 citation statements)

References 30 publications

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“…N-Alkylphthalimides exhibit fluorescence with remarkable low quantum yields of Φ f ) 0.01 or less in solution at room temperature. 3,15 For 5 in acetonitrile, where λ f ) 390 nm, Φ f ) 8 × 10 -4 , and the lifetime τ f ) 0.19 ns, the rate constants are k f ) 4 × 10 6 s -1 and k isc ) 4 × 10 9 s -1 . 22 The fluorescence is even lower for 5 and N-propylphthalimide in aprotic media.…”

Section: Photolysismentioning

confidence: 99%

Photodecarboxylation Study of Carboxy-Substituted N-Alkylphthalimides in Aqueous Solution: Time Resolved UV−Vis Spectroscopy and Conductometry

2002

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The photophysical and photochemical properties of N-phthaloyltranexamic acid (3b) and N-methylsulfanylmethylphthalimide (4e) as well as several sulfur-containing carboxylates, N-phthaloylmethionine (1), N-phthaloyl-S-carboxymethylcysteine (2c), phthalimidomethylsulfanyl acetic acid (4a), and its derivatives 4b-4d were studied in aqueous solution by time-resolved UV-vis spectroscopy and conductivity using laser pulses at 248 or 308 nm. From the changes in absorption spectra upon continuous irradiation at 290 nm, the quantum yields of substrate decomposition (Φ d ) were measured for various cases. The quantum yields of formation of the lowest triplet state (Φ isc ) are small, when Φ d is large and vice versa. The quantum yields of decarboxylation, Φ(-CO 2 ), were determined by conductometry. Φ(-CO 2 ) is largest (0.3) for 3b in argonsaturated aqueous solution at pH 6-10 and decreases in the order 4a-c, 2c, 1, and 4d. The increase of Φ d vs pH indicates that carboxylic acids exhibit low decarboxylation efficiencies, whereas the corresponding anions effectively eliminate CO 2 and subsequently cyclize. The mechanisms of photochemical decomposition, decarboxylation, and cyclization are discussed.

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Section: Photolysismentioning

confidence: 99%

Photodecarboxylation Study of Carboxy-Substituted N-Alkylphthalimides in Aqueous Solution: Time Resolved UV−Vis Spectroscopy and Conductometry

2002

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“…Parallel to our investigations of the photochemistry of alkyl-substituted amino acids, we have also studied heteroatom-substituted amino acids (serine [5], threonine [ 5 ] , methionine [6], cysteine [7]) and aryl-substituted amino acids (phenylalanine, tyrosine, DOPA (= 3-hydroxytyrosine) [5]). The presence of easily oxidizable groups in the substrates led to significant changes in the chemoselectivity : the C-terminal-unprotected a-amino acids were decarboxylated only partially when directly excited or triplet-sensitized.…”

Section: Synthesis Of Medium-andmentioning

confidence: 99%

“…solvent but led to a decrease in conversion. We, therefore, assume that the excited triplet is the reactive species, similar by to other PET reactions with the phthalimide chromophore as the electron-accepting part and acetone as the triplet sensitizer [5] [7]. In a relatively broad concentration window, the amount of H,O did not influence the rate of substrate conversion, but strongly the product ratio 5e/6e.…”

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confidence: 98%

Synthesis of Medium‐ and Large‐Ring Compounds Initiated by Photochemical Decarboxylation of ω‐Phthalimidoalkanoates

Griesbeck

Henz

Krämer

et al. 1997

Helvetica Chimica Acta

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The synthesis of a variety of hydroxylactams from w-phthalimidoalkanoates using a triplet-sensitized photodecarboxylation reaction initiated by intramolecular photo electron transfer is described. Ring sizes available by this method span from 4 (benzazepine-1,5-dione 7) to 26 (cyclodipeptide 26e). Ground-state template formation is proposed as the explanation for the high efficiency of this reaction and for the decrease in reactivity in the presence of organic bases instead of metal carbonates. The crucial step in this macrocyclization reaction seems to be the protonation of the intermediary ketyl radials (Scheme 4). Spacer groups investigated were alkyl chains (C3-Cll: 5c-h, lla, 12), ether (16, 18), ester (20, 22), and amide (26a-f) linkages. Within the detection limits, no dimeric (= decarboxylative coupling) products were observed, indicating the high preference for intravs. intermolecular photoelectron transfer. The C,C radical combination step proceeds with low stereoselectivity (cJ products 11 and 12) in contrast to comparable singlet reactions. Except for the lactones 22, all products were stable under the photolysis conditions. Prolonged irradiation of 22 led to the formation of the spiro compounds 23, probably via an intermediary acyliminium betaine (Scheme 8). One serious limitation of the decarboxylative macrocyclization is its incompatibility with the glycine spacer (as in 27a and 27b), probably the consequence of a strong intramolecular H-bond (Scheme 10).

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“…Several photochemical approaches starting with suitably substituted N-alkylphthalimides and silylalkyl analogues, involving a hydroxyazetidine intermediate that opens to give the expanded benzazepinedione ring, have been developed. [18Ϫ23] These photoprocesses follow various pathways that include Norrish type II or sequential SET desilylation reactions followed by Yang cyclization, [24Ϫ27] ω-hydrogen abstraction/elimination, [28,29] single-electron transfer (SET) together with proton transfer [30,31] and SET followed by decarboxylative photocyclization. [32] A more convergent approach is provided by the intermolecular photocycloaddition of alkenes to the C(O)ϪN bond of N-methylphthalimide (NMP).…”

Section: Introductionmentioning

confidence: 99%

Photocycloaddition of Phthalimide Anion to Alkenes − A Highly Efficient, Convergent Method for [2]Benzazepine Synthesis

et al. 2002

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The excited state of phthalimide anion adds to cyclic, acyclic and aryl-conjugated alkenes in an efficient and regioselective manner to form [2]benzazepine-1,5-diones, substituted at positions 3 and/or 4. The reaction is independent of the ionization potential of the alkene. This process contrasts with the related reactions of N-methylphthalimide or phthalimide, which are limited by the requirement that the participating

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Photochemistry of N-phthaloyl derivatives of electron-donor-substituted amino acids

Cited by 42 publications

References 30 publications

Photodecarboxylation Study of Carboxy-Substituted N-Alkylphthalimides in Aqueous Solution: Time Resolved UV−Vis Spectroscopy and Conductometry

Photodecarboxylation Study of Carboxy-Substituted N-Alkylphthalimides in Aqueous Solution: Time Resolved UV−Vis Spectroscopy and Conductometry

Synthesis of Medium‐ and Large‐Ring Compounds Initiated by Photochemical Decarboxylation of ω‐Phthalimidoalkanoates

Photocycloaddition of Phthalimide Anion to Alkenes − A Highly Efficient, Convergent Method for [2]Benzazepine Synthesis

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