Cis/trans conversion of potassium derivatives of 2- and 4-nitrostilbenes

Todres, Z. V.

doi:10.1016/0022-328x(92)80165-t

Cited by 12 publications

(4 citation statements)

References 4 publications

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“…At this stage, rotation around the weakened C=C double bond can occur. We have previously suggested such possibility based on general orbital considerations [36][37][38], however, we recently became aware that trans-cis isomerization of β-nitrostyrenes has indeed been experimentally observed upon generation of the corresponding radical anion [67]. This older report supports the validity of our proposal.…”

Section: Optimization Of the Reaction Conditionssupporting

confidence: 79%

Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate

2022

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The reductive cyclization of suitably substituted organic nitro compounds by carbon monoxide is a very appealing technique for the synthesis of heterocycles because of its atom efficiency and easiness of separation of the only stoichiometric byproduct CO2, but the need for pressurized CO has hampered its diffusion. We have recently reported on the synthesis of indoles by reductive cyclization of o-nitrostyrenes using phenyl formate as a CO surrogate, using a palladium/1,10-phenanthroline complex as catalyst. However, depending on the desired substituents on the structure, the use of β-nitrostyrenes as alternative reagents may be advantageous. We report here the results of our study on the possibility to use phenyl formate as a CO surrogate in the synthesis of indoles by reductive cyclization of β-nitrostyrenes, using PdCl2(CH3CN)2 + phenanthroline as the catalyst. It turned out that good results can be obtained when the starting nitrostyrene bears an aryl substituent in the alpha position. However, when no such substituent is present, only fair yield of indole can be obtained because the base required to decompose the formate also catalyzes an oligo-polymerization of the starting styrene. The reaction can be performed in a single glass pressure tube, a cheap and easily available piece of equipment.

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Section: Optimization Of the Reaction Conditionssupporting

confidence: 79%

Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate

2022

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“…Additionally, high K 2 CO 3 concentrations result in the formation of a poorly soluble yellow powder and the disappearance of part of the trans-β-nitrostyrene from the solution; as evidenced by NMR spectroscopy. Most likely, this precipitate is the result of complexation between K + and the nitro-moiety, 18 which is corroborated by the fact that this precipitate dissolves again when 18-crown-6 is added. The catalytic activity of NaPy in the presence of other salts such as CaCO 3 , Na 2 CO 3 , and KCl is low ( Figure 6B), with the exception of Cs 2 CO 3 (see ESI Figure S10 for 1 H NMR data).…”

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confidence: 89%

Scope and Limitations of Supramolecular Autoregulation

Teunissen

Haas

Vekemans

et al. 2016

Bulletin of the Chemical Society of Japan

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Recently, our group has reported on the ureidopyrimidinone (UPy) induced buffering of 2,7-diamido-1,8-naphthyridine (NaPy) and used this phenomenon to regulate the catalysis of the Michael addition of 2,4-pentanedione to trans-β-nitrostyrene. We now show that the observed catalytic activity of NaPy is the result of a strong synergy between NaPy and trace amounts of K 2 CO 3 , resulting in a more than 100-fold increase in reaction rate compared to the two compounds separately. By keeping the concentration of K 2 CO 3 , as well as NaPy, constant, an improved regulation of the catalytic activity is achieved. We show that the catalytic activity can be precisely regulated in a noncovalent manner via the addition of the UPy motif. Finally, different salts and Michael substrates are screened to assess the selectivity of this catalytic couple and to provide a platform for future research in molecular buffering, regulation, and chemical networks.

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“…In contrast, a spectrum displaying significantly more complicated hyperfine interactions was observed when KO t ‐Bu was employed (Figure 1 b). [21, 22] Simulation of the spectra with a variety of possible radicals revealed a best match when assuming a mixture of 93 % of 8 and 7 % of 9 . We interpret these data to suggest that the nitro radical is less effective in coordinating the larger potassium counterion.…”

Section: Resultsmentioning

confidence: 97%

Counterion Control oft‐BuO‐Mediated Single Electron Transfer to Nitrostilbenes to ConstructN‐Hydroxyindoles or Oxindoles

et al. 2021

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tert‐Butoxide unlocks new reactivity patterns embedded in nitroarenes. Exposure of nitrostilbenes to sodium tert‐butoxide was found to produce N‐hydroxyindoles at room temperature without an additive. Changing the counterion to potassium changed the reaction outcome to yield solely oxindoles through an unprecedented dioxygen‐transfer reaction followed by a 1,2‐phenyl migration. Mechanistic experiments established that these reactions proceed via radical intermediates and suggest that counterion coordination controls whether an oxindole or N‐hydroxyindole product is formed.

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Cis/trans conversion of potassium derivatives of 2- and 4-nitrostilbenes

Cited by 12 publications

References 4 publications

Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate

Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate

Scope and Limitations of Supramolecular Autoregulation

Counterion Control oft‐BuO‐Mediated Single Electron Transfer to Nitrostilbenes to ConstructN‐Hydroxyindoles or Oxindoles

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