An unusual thermal oxidation of triaryloxazoles

Pickett, James E.

doi:10.1016/j.tetlet.2014.10.072

Cited by 6 publications

(3 citation statements)

References 23 publications

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“…Again, because O 2 addition onto a C¼C bond is spin forbidden, intersystem crossing is necessary, and it is probably achieved by an energy shift in the π orbitals of the 2,3enediolate allowing a triplet-to-singlet transition. Similar transitions have been found in non-enzymatic, light-independent reactions of O 2 addition on enolic compounds, with energy barriers of 87-96 kJ mol À1 (Najjar et al 2005;Triquigneaux et al 2010;Kholdeeva et al 2011;Pickett 2014). Peroxidation of methyl naphtol has a rate constant at standard substrate concentration of about 6.5 × 10 À4 s À1 (Kholdeeva et al 2011), i.e.…”

Section: Most Likely Chemical Events and Energy Profilesupporting

confidence: 63%

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The mechanism of Rubisco‐catalysed oxygenation

Tcherkez

2015

Plant Cell & Environment

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Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the cornerstone of photosynthetic carbon assimilation because it catalyses the fixation of CO2 onto ribulose-1,5-bisphosphate (RuBP). The enzyme also catalyses RuBP oxygenation, thereby evolving phosphoglycolate which is recycled along the photorespiratory pathway. Oxygenation is quantitatively important, because under ordinary gaseous conditions, more than one third of RuBP molecules are oxygenated rather than carboxylated. However, contrary to carboxylation, the chemical mechanism of oxygenation is not well known, and little progress has been made since the early 80s. Here, I review recent experimental data that provide some new insights into the reaction mechanism, and carry out simple calculations of kinetic parameters. Isotope effects suggest that oxygenation is less likely initiated by a redox phenomenon (such as superoxide production) and more likely involves concerted chemical events that imply interactions with protons. A possible energy profile of the reaction is drawn which suggests that the generation of the oxygenated reaction intermediate (peroxide) is irreversible. Possible changes in oxygenation-associated rate constants between Rubisco forms are discussed.

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Section: Most Likely Chemical Events and Energy Profilesupporting

confidence: 63%

“…; Kholdeeva et al . ; Pickett ). Peroxidation of methyl naphtol has a rate constant at standard substrate concentration of about 6.5 × 10 −4 s −1 (Kholdeeva et al .…”

Section: Most Likely Chemical Events and Energy Profilementioning

confidence: 89%

The mechanism of Rubisco‐catalysed oxygenation

Tcherkez

2015

Plant Cell & Environment

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“…During our initial experiments under the optimized conditions, trace amounts of N-formylbenzamide were simultaneously formed. We rationalized this outcome with the reaction of oxazole aldehyde with singlet oxygen ( 1 O 2 ) to give the ring opening product imide [27] as the 9-mesityl acridinium salts 3 display the capacity of efficient singlet oxygen formation. [28] Thus, the formation of 1 O 2 in this photocatalytic aerobic cyclization of N-propargylamides was investigated.…”

Section: Resultsmentioning

confidence: 99%

Photocatalytic Aerobic Cyclization of N‐Propargylamides Enabled by Selenium‐π‐Acid Catalysis

Wang

Jiang

Zhang

et al. 2023

Chemistry A European J

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A dual catalytic approach combining photocatalyst and selenium‐π‐acid synergy has been used to cyclized of N‐propargylamides. This method offers readily access to oxazole aldehydes under chemical oxidant‐free conditions with low catalyst loadings, where air acts as a terminal and gratuitous oxidant. The reaction is demonstrated with a range of substrates, including aryl and alkyl propargyl amides, and in the late‐stage functionalization of several amide‐containing drug molecules. Mechanistic studies suggest that the acridinium catalyst is able to oxidize diselenide and generate singlet oxygen (1O2), which is responsible for this transformation.

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Palladium‐Catalyzed Chemo‐ and Enantioselective C−O Bond Cleavage of α‐Acyloxy Ketones by Hydrogenolysis

et al. 2016

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Ac hemoselective C À Ob ond cleavage of the ester alkylside-chain of a-acyloxy ketones was realized for the first time by ah ighly efficient palladium-catalyzed hydrogenolysis (S/C = 6000, the highest catalytic efficiency by far). Furthermore,akinetic resolution of a-acyloxy ketones was first developed by enantioselective hydrogenolysis with good yields and up to 99 %ee.Supportinginformation for this article can be found under: http://dx.

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An unusual thermal oxidation of triaryloxazoles

Cited by 6 publications

References 23 publications

The mechanism of Rubisco‐catalysed oxygenation

The mechanism of Rubisco‐catalysed oxygenation

Photocatalytic Aerobic Cyclization of N‐Propargylamides Enabled by Selenium‐π‐Acid Catalysis

Palladium‐Catalyzed Chemo‐ and Enantioselective C−O Bond Cleavage of α‐Acyloxy Ketones by Hydrogenolysis

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