Structure of the Radicals Formed in the Mitsunobu Reaction.

Eberson, Lennart; Persson, Ola; Svensson, Jan‐Olof; Gumm, Andreas; Larsen, Sine

doi:10.3891/acta.chem.scand.52-1293

Cited by 19 publications

(19 citation statements)

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“…However, a subsequent investigation by Eberson et al using cyclic voltammetry has shown that the structure of this radical cation is more consistent with the P-O adduct 3. 9 Eberson's evidence is compelling and we agree with this re-assignment.…”

Section: Resultssupporting

confidence: 69%

“…It should be noted that the first step in Scheme 3 (the SET to generate 8, the most likely precursor of 7) has been shown by Eberson to be far too endergonic to be realistic under any conditions. 9 It is more likely that 8 is generated during the oxida-tion of the betaine by DIAD or DEAD (the SET step to generate 3, see Scheme 1). However, when 8 was generated in the presence of DIAD by other means, 7,16b we saw no evidence of formation of the radical responsible for the 9-line spectrum.…”

Section: Scheme 3 Possible Mechanism For Formation Of a Radical Anionmentioning

confidence: 99%

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Formation of an Unusual Four-Membered Nitrogen Ring (Tetrazetidine) Radical Cation

et al. 2012

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Treatment of triphenylphosphine (Ph(3)P) with an excess of diisopropyl azodicarboxylate at 0-25 °C resulted in the formation of a symmetrical tetraalkyl tetrazetidinetetracarboxylate radical cation, containing the elusive cyclic N(4) ring system. Electron paramagnetic resonance (EPR) spectroscopy revealed a 9-line spectrum, with hyperfine coupling constants indicative of four almost magnetically equivalent nitrogen atoms. The radical species was surprisingly long-lived, and could still be observed several hours after generation and standing at 25 °C. Expansion of the central resonance revealed further splitting into a pentet (hyperfine coupling to the four methine protons). Three mechanistically plausible structures containing the tetrazetidine substructure were proposed based on the 9-line EPR spectrum. Following DFT calculations, the predicted hyperfine coupling constants were used to simulate the EPR spectra for the three candidate structures. The combined calculations and simulations were consistent with a radical cation species, but not a radical anion or radical-carbenoid structure. The lowest energy conformation of the N(4) ring was slightly puckered, with the alkyl carboxylate groups all trans and the four carbonyl groups aligned in a pinwheel arrangement around the ring. Analogous results were obtained with the original Mitsunobu reagents, Ph(3)P and diethyl azodicarboxylate, but not with Ph(3)P and di-tert-butyl azodicarboxylate. A mechanism is proposed based on a radical version of the Rauhut-Currier or Morita-Baylis-Hillman reactions.

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Section: Resultssupporting

confidence: 69%

Section: Scheme 3 Possible Mechanism For Formation Of a Radical Anionmentioning

confidence: 99%

Formation of an Unusual Four-Membered Nitrogen Ring (Tetrazetidine) Radical Cation

et al. 2012

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“…Considering the redox potential of amines17 and azodicarboxylate esters,18 both oxidation of amines and reduction of azodicarboxylate esters by excited photocatalyst19 are possible. To obtain mechanistic insight into the electron‐transfer process, we investigated fluorescence quenching studies of 4 a in the presence of 1 a or 2 a in NMP.…”

Section: Resultsmentioning

confidence: 99%

Direct sp³ CH Amination of Nitrogen‐Containing Benzoheterocycles Mediated by Visible‐Light‐Photoredox Catalysts

Miyake

Nakajima

Nishibayashi

2012

Chemistry A European J

104

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“…This provides an indirect approach for α-C–H functionalization of N -aryltetrahydroquinolines and N -arylindolines. Based on the feasibility of oxidation of aromatic amines as well as reduction of di- tert -butyl azodicarboxylate ( 110 ) by the photoexcited Ir(III) complex [98–99], the authors favored a mechanism that does not involve the direct addition of α-amino radical 112 to di- tert -butyl azodicarboxylate ( 110 ). Oxidation of N -phenyltetrahydroquinoline by the photoexcited Ir(III) complex followed by deprotonation provides α-amino radical 112 with the concomitant formation of the Ir(II) complex.…”

Section: Reviewmentioning

confidence: 99%

The chemistry of amine radical cations produced by visible light photoredox catalysis

Hu¹,

Wang²,

Nguyen³

et al. 2013

Beilstein J. Org. Chem.

397

228

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Amine radical cations are highly useful reactive intermediates in amine synthesis. They have displayed several modes of reactivity leading to some highly sought-after synthetic intermediates including iminium ions, α-amino radicals, and distonic ions. One appealing method to access amine radical cations is through one-electron oxidation of the corresponding amines under visible light photoredox conditions. This approach and subsequent chemistries are emerging as a powerful tool in amine synthesis. This article reviews synthetic applications of amine radical cations produced by visible light photocatalysis.1977

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Structure of the Radicals Formed in the Mitsunobu Reaction.

Cited by 19 publications

References 0 publications

Formation of an Unusual Four-Membered Nitrogen Ring (Tetrazetidine) Radical Cation

Formation of an Unusual Four-Membered Nitrogen Ring (Tetrazetidine) Radical Cation

Direct sp³ CH Amination of Nitrogen‐Containing Benzoheterocycles Mediated by Visible‐Light‐Photoredox Catalysts

The chemistry of amine radical cations produced by visible light photoredox catalysis

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Structure of the Radicals Formed in the Mitsunobu Reaction.

Cited by 19 publications

References 0 publications

Formation of an Unusual Four-Membered Nitrogen Ring (Tetrazetidine) Radical Cation

Formation of an Unusual Four-Membered Nitrogen Ring (Tetrazetidine) Radical Cation

Direct sp3 CH Amination of Nitrogen‐Containing Benzoheterocycles Mediated by Visible‐Light‐Photoredox Catalysts

The chemistry of amine radical cations produced by visible light photoredox catalysis

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Direct sp³ CH Amination of Nitrogen‐Containing Benzoheterocycles Mediated by Visible‐Light‐Photoredox Catalysts