Photochemistry of 5-methylphenazinium salts in aqueous solution. 2. Optical flash photolysis and fluorescence results and a proposed mechanism

Chew, Vivian S. F.; Bolton, James R.; Brown, Robert G.; Porter, George

doi:10.1021/j100452a009

Cited by 27 publications

(3 citation statements)

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“…Phenazinium salts are a well-known electron acceptor in enzymatic assays . Many studies have proven the existence of radical 6 . It was shown to be unstable in a basic environment and would disproportionate to give the doubly reduced hydrophenazine 7 . , Photocatalyst 1i was then regenerated by the oxidation of hydrophenazine 7 with O 2 in sequential steps.…”

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confidence: 99%

Phenazinium Salt-Catalyzed Aerobic Oxidative Amidation of Aromatic Aldehydes

Leow

2014

Org. Lett.

104

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Amides are prevalent in organic synthesis. Developing an efficient synthesis that avoids expensive oxidants and heating is highly desirable. Here the oxidative amidation of aromatic aldehydes is reported using an inexpensive metal-free visible light photocatalyst, phenazine ethosulfate, at low catalytic loading (1-2 mol %). The reaction proceeds at ambient temperature and uses air as the sole oxidant. The operationally easy procedure provides an economical, green, and mild alternative for the formation of amide bonds.

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confidence: 99%

Phenazinium Salt-Catalyzed Aerobic Oxidative Amidation of Aromatic Aldehydes

Leow

2014

Org. Lett.

104

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“…However, this effect was not manifest at high concentrations of TMPD or DCPIP. The likely explanation is that the semireduced radical of PMS formed due to its photo-induced oxidation [18] can act as a weak uncoupler-protonophore and slightly accelerate the passive k~ discharging through the proteoliposome membrane. Fig.…”

Section: Resultsmentioning

confidence: 99%

Electrogenic reduction of the primary electron donor P700⁺ in photosystem I by redox dyes

et al. 1997

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The kinetics of reduction of the photo-oxidized primary electron donor P700 + by redox dyes N,N,N',N'-tetr amethyl-p-phenylendiamine, 2,6-dichlorophenoMndophenol and phenazine methosulfate was studied in proteoliposomes containing Photosystem I complexes from cyanobacteria Synechocystis sp. PCC 6803 using direct electrometrical technique, in the presence of high concentrations of redox dyes, the fast generation of a membrane potential related to electron transfer between P700 and the terminal iron-sulfur clusters FA/FB was followed by a new electrogenic phase in the millisecond time domain, which contributes approximately 20% to the overall photoelectric response. This phase is ascribed to the vectorial transfer of an electron from the redox dye to the proteinembedded chlorophyll of P700 +. Since the contribution of this electrogenic phase in the presence of artificial redox dyes is approximately equal to that of the phase observed earlier in the presence of cytochrome co, it is likely that electrogenic reduction of P700 + in vivo occurs due to vectorial electron transfer within RC molecule rather than within the cytochrome c6-P700 complex.© 1997 Federation of European Biochemical Societies.

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“…adduct during the visible irradiation of air saturated solutions of food dyes (Carmichael et al,198Sa). This type of intermediate has been postulated to exist in the photochemistry of 5-methylphenazinium salts in aqueous solutions (Chew et al, 1980). Presumably, these hydrated intermediates act as strong oxidizing agents and appear to react as .OH radical addition reagents.…”

Section: Aerobic Photolysismentioning

confidence: 96%

PHOTOCHEMISTRY OF AQUEOUS ADRIAMYCIN AND DAUNOMYCIN. A SPIN TRAPPING STUDY WITH ¹⁷O ENRICHED OXYGEN AND WATER

Alegrı́a¹,

Riesz²

1988

Photochem & Photobiology

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Photolyses at 485 or 490 nm of air saturated, H,I7O enriched, aqueous solutions of adriamycin (ADR) in the presence of 5,5-dimethyl-l-pyrroline-l-oxide (DMPO) produce a mixture of hydroxyl radical spin-adducts, i.e. DMPO-I"OH. and DMPO-I70H., as detected by electron spin resonance (ESR). DMPO-I70H. was also observed during the irradiation at these same wavelengths of aqueous solutions of ADR or daunomycin (DA) containing DMPO and 170 enriched oxygen. Therefore, the observed hydroxyl radical spin-adducts derive from both water and gaseous oxygen. It is concluded from the measured relative spin-adduct concentrations and from the enrichment fractions that most of the DMPO-OH adducts originate from water. However, if anaerobic diluted solutions of ADR (200 p M ) or DA (600 p M ) in the presence of DMPO (13 mM and 27 mM respectively) are irradiated at these same wavelengths no spin adduct is detected, indicating that oxygen is needed for the adduct formation, at these drug and spin trap concentrations. DMPO-OH. is always observed if relatively high concentrations of either the drug (1.1-2.9 mM) or the spin trap (100-150 mM) are used in argon saturated solutions. A water photooxidation mediated mechanism is proposed in order to account for these results, analogous to previous observations in the photochemistry of other water soluble anthraquinone derivatives.

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Photochemistry of 5-methylphenazinium salts in aqueous solution. 2. Optical flash photolysis and fluorescence results and a proposed mechanism

Cited by 27 publications

References 9 publications

Phenazinium Salt-Catalyzed Aerobic Oxidative Amidation of Aromatic Aldehydes

Phenazinium Salt-Catalyzed Aerobic Oxidative Amidation of Aromatic Aldehydes

Electrogenic reduction of the primary electron donor P700⁺ in photosystem I by redox dyes

PHOTOCHEMISTRY OF AQUEOUS ADRIAMYCIN AND DAUNOMYCIN. A SPIN TRAPPING STUDY WITH ¹⁷O ENRICHED OXYGEN AND WATER

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Photochemistry of 5-methylphenazinium salts in aqueous solution. 2. Optical flash photolysis and fluorescence results and a proposed mechanism

Cited by 27 publications

References 9 publications

Phenazinium Salt-Catalyzed Aerobic Oxidative Amidation of Aromatic Aldehydes

Phenazinium Salt-Catalyzed Aerobic Oxidative Amidation of Aromatic Aldehydes

Electrogenic reduction of the primary electron donor P700+ in photosystem I by redox dyes

PHOTOCHEMISTRY OF AQUEOUS ADRIAMYCIN AND DAUNOMYCIN. A SPIN TRAPPING STUDY WITH 17O ENRICHED OXYGEN AND WATER

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Electrogenic reduction of the primary electron donor P700⁺ in photosystem I by redox dyes

PHOTOCHEMISTRY OF AQUEOUS ADRIAMYCIN AND DAUNOMYCIN. A SPIN TRAPPING STUDY WITH ¹⁷O ENRICHED OXYGEN AND WATER