Photocatalytic Oxidative Heterocyclization of Semicarbazones: An Efficient Approach for the Synthesis of 1,3,4-Oxadiazoles

Kapoorr, Ritu; Singh, Sachchida N.; Tripathi, Shubhangi; Yadav, Lal Dhar S.

doi:10.1055/s-0034-1380493

Cited by 31 publications

(5 citation statements)

References 19 publications

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“…† Selective N-methylation of the quinuclidine N (N1) is achieved by treating Qn with MeI at room temperature, 28 giving MeQn + , whereas a reaction temperature of 100 C leads to Me 2 Qn 2+ by N-methylation of both N1 and the quinoline N (N2). 29,30 This selectivity follows the known basicity trend of N1 and N2. 21,31,32 Methylation at each site gives characteristic changes in 1 H NMR chemical shis ( Fig.…”

Section: Resultsmentioning

confidence: 53%

Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield

et al. 2020

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Section: Resultsmentioning

confidence: 53%

Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield

et al. 2020

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“…Yadav et al reported the synthesis of 1,3,4-oxadiazoles from aldehyde semicarbazones, using CBr 4 , green LEDs and Eosin Y as the photocatalyst, at room temperature, in the presence of air (Scheme 18) [63]. …”

Section: Reviewmentioning

confidence: 99%

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

Bogdos¹,

Pinard²,

Murphy³

2018

Beilstein J. Org. Chem.

105

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The focus of this review is to provide an overview of the field of organocatalysed photoredox chemistry relevant to synthetic medicinal chemistry. Photoredox transformations have been shown to enable key transformations that are important to the pharmaceutical industry. This type of chemistry has also demonstrated a high degree of sustainability, especially when organic dyes can be employed in place of often toxic and environmentally damaging transition metals. The sections are arranged according to the general class of the presented reactions and the value of these methods to medicinal chemistry is considered. An overview of the general characteristics of the photocatalysts as well as some electrochemical data is presented. In addition, the general reaction mechanisms for organocatalysed photoredox transformations are discussed and some individual mechanistic considerations are highlighted in the text when appropriate.

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“…Selective N-methylation of the quinuclidine N (N1) is achieved by treating Qn with MeI at room temperature, 27 giving MeQn + , whereas a reaction temperature of 100 °C leads to Me2Qn 2+ by N-methylation of both N1 and the quinoline N (N2). 28,29 This selectivity follows the known basicity trend of N1 and N2. 20,30,31 Methylation at each site gives characteristic changes in 1 H NMR chemical shifts (Figs.…”

Section: Resultsmentioning

confidence: 54%

Modulation of Charge Transfer by N-Alkylation to Control Photoluminescence Energy and Quantum Yield

Turley¹,

Danos²,

Prlj³

et al. 2020

Preprint

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Charge transfer in organic fluorophores is a fundamental photophysical process that can be either beneficial, e.g., facilitating thermally activated delayed fluorescence, or detrimetnal, e.g., mediating emission quenching. N-Alkylation is shown to provide straightforward synthetic control of the charge transfer, emission energy and quantum yield of amine chromophores. We demonstrate this concept using quinine as a model. N-Alkylation causes changes in its emission that mirror those caused by changes in pH (i.e., protonation). Unlike protonation, however, alkylation of quinine’s two N sites is performed in a stepwise manner to give kinetically stable species. This kinetic stability allows us to isolate and characterize an N-alkylated analog of an ‘unnatural’ protonation state that is quaternized selectively at the less basic site, which is inaccessible using acid. These materials expose (i) the through-space charge-transfer excited state of quinine and (ii) the associated loss pathway, while (iii) developing a simple salt that outperforms quinine sulfate as a quantum yield standard. This N-alkylation approach can be applied broadly in the discovery of emissive materials by tuning charge-transfer states.

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Photocatalytic Oxidative Heterocyclization of Semicarbazones: An Efficient Approach for the Synthesis of 1,3,4-Oxadiazoles

Cited by 31 publications

References 19 publications

Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield

Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

Modulation of Charge Transfer by N-Alkylation to Control Photoluminescence Energy and Quantum Yield

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