Evidence for electron transfer in the photochemistry of .pi.-.pi.* triplet states

Padwa, Albert; Eisenhardt, William; Gruber, Robert; Pashayan, Deran

doi:10.1021/ja01035a050

Cited by 30 publications

(10 citation statements)

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“…This pathway is illustrated below in the reported transformation of the bis(pyrrolidinyl) quinone, III → IV . Other interesting examples of charge-transfer intermediates that are responsible for rearrangement or fragmentation reactions include cyclization analogous to III → IV for 2-chloro-3-(dimethylamino)-1,4-naphthoquinone and the alternative electron-transfer mechanism proposed for Norrish type II photoelimination of α-aminoketones …”

Section: Resultsmentioning

confidence: 99%

“…Other interesting examples of charge-transfer intermediates that are responsible for rearrangement or fragmentation reactions include cyclization analogous to III f IV for 2-chloro-3-(dimethylamino)-1,4-naphthoquinone 25 and the alternative electron-transfer mechanism proposed for Norrish type II photoelimination of R-aminoketones. 26 In summary, quinone conjugates of simple amino acids alanine and proline act as reversible electron-transfer acceptors. Their photochemistry is dominated by intramolecular electrontransfer reactions that occur via a low-lying charge transfer (ICT) excited state.…”

Section: Resultsmentioning

confidence: 99%

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Photochemistry of Quinone-Bridged Amino Acids. Intramolecular Trapping of an Excited Charge-Transfer State

Jones

Qian

1998

J. Phys. Chem. A

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Linkages to amino acids that feature a chlorinated p-benzoquinone as a bridging group have been prepared by reaction of 2,5-dichloro-p-benzoquinone or chloranil with the free amine groups of alanine and proline. Electron-transfer capabilities of these peptide conjugates have been assessed through cyclic voltammetry and laser flash photolysis measurements. Phototransients are observed (λ max ) 410 nm) that cannot be assigned to either triplet or radical anion intermediates normally associated with quinones. These intermediates are associated with novel biradical zwitterions that result from intramolecular trapping of an aminoquinone excited charge-transfer (CT) state.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Photochemistry of Quinone-Bridged Amino Acids. Intramolecular Trapping of an Excited Charge-Transfer State

Jones

Qian

1998

J. Phys. Chem. A

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“…The seventh component (15) (aldehyde CH stretch), 5.86 (aldehyde C=0), and 5.95 µ (benzoyl C=0); its ultraviolet spectrum showed maxima at 242 and 278 µ. Its nmr spectrum revealed several important points, specifically, the presence of an uncoupled aldehyde proton and five (extensively coupled) saturated hydrogens.…”

Section: Resultsmentioning

confidence: 99%

Photochemical transformations of small ring carbonyl compounds. XXX. Electron transfer in the photochemistry of azetidinyl ketones

Padwa¹,

Albrecht²,

Singh³

et al. 1971

J. Am. Chem. Soc.

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“…More facile than γ Hradical abstraction is quenching of the triplet excited state through a rapid electron transfer from nitrogen to form a ketyl radical, which opens up a more favorable degradation pathway through the scission of the C -N bond, yielding methylketones and imine oligomers, or amines through complex reductive processes (Figure 2B). 17,18 One way to avoid this has been to protect the amine so that its lone pair engages in conjugation with other groups (e.g. by converting it to amides, carbamates, sulfonamides; Figure 2C), [19][20][21] but this necessitates additional steps (introduction and removal of the electron-withdrawing group) and precludes the use of tertiary amines.…”

Section: General Observationsmentioning

confidence: 99%

Aza-Yang Cyclization—Buchner Aromatic Ring Expansion: Collective Synthesis of Cycloheptatriene-containing Azetidine Lactones

Singh

Gaskins

Johnson

et al. 2021

Preprint

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We prepared a collection of complex cycloheptatriene-containing azetidine lactones by ap- plying two key photochemical reactions: “aza-Yang” cyclization and Buchner carbene insertion into aromatic rings. While photolysis of phenacyl amines leads to a rapid charge transfer and elimination, we found that a simple protonation of the amine enables the formation of azetidinols as single diastereomers. We provide evidence, through ultrafast spectroscopy, for the electron transfer from free amines in the excited state. Further, we characterize aza-Yang re- action by establishing the dependence of initial reaction rates on rates of photon absorption. Unanticipated change in reactivity in morpholine analogs is explained through interactions with the tosylate anion. Buchner reaction proceeds with slight preference for one diastereomer over the other, and successful reaction requires electron-donating carbene-stabilizing substituents. Overall, sixteen compounds were prepared over seven steps. Guided by an increase in structural complexity, efforts such as this one extend reach of chemists into unexplored chemical space and provide useful quantities of new compounds for studies focused on their properties.

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Evidence for electron transfer in the photochemistry of .pi.-.pi.* triplet states

Cited by 30 publications

References 1 publication

Photochemistry of Quinone-Bridged Amino Acids. Intramolecular Trapping of an Excited Charge-Transfer State

Photochemistry of Quinone-Bridged Amino Acids. Intramolecular Trapping of an Excited Charge-Transfer State

Photochemical transformations of small ring carbonyl compounds. XXX. Electron transfer in the photochemistry of azetidinyl ketones

Aza-Yang Cyclization—Buchner Aromatic Ring Expansion: Collective Synthesis of Cycloheptatriene-containing Azetidine Lactones

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