Catalytic Action of Azolium Salts. VIII. Oxidative Aroylation with Arenecarbaldehydes Catalyzed by 1,3-Dimethylbenzimidazolium Iodide.

Miyashita, Akira; Suzuki, Yumiko; Nagasaki, Izuru; Ishiguro, Chie; Iwamoto, Kaoru; Higashino, Takeo

doi:10.1248/cpb.45.1254

Cited by 71 publications

(36 citation statements)

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“…Several reports exist of thiazolium or benzimidazolium reagents catalyzing the oxidation of aromatic aldehydes to esters. 29–33,35 A representative example is the recent disclosure by Connon and co-workers of an approach utilizing a thiazolium catalyst and azobenzene as an oxidant 55. While this method gives good yields for the oxidation of substituted benzaldehydes (46–97% yield, 8 substrates), application to unactivated substrates results in poor yields of the ester.…”

Section: Resultsmentioning

confidence: 99%

“…Using a non-enzymatic thiazolium-based N -heterocyclic carbene (NHC), very brief studies concerning the oxidative transformation converting aromatic aldehydes to esters were reported 29–32. More recently, Miyashita33 has demonstrated that other NHCs derived from triazolium and benzimidazolium salts, are capable of catalyzing the oxidation of aryl aldehydes. These processes generally employed organic oxidants such as substituted nitrobenzenes, azobenzene derivatives, and flavin.…”

Section: Introductionmentioning

confidence: 99%

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N-Heterocyclic carbene-catalyzed oxidations

et al. 2009

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N-Heterocyclic carbenes catalyze the oxidation of allylic and benzylic alcohols as well as saturated aldehydes to esters with manganese(IV) oxide in excellent yields. A variety of esters can be synthesized, including protected carboxylates. The oxidation proceeds under mild conditions, with low loadings of a simple triazolium salt pre-catalyst in the presence of base. Substrates containing potentially epimerizable centers are oxidized while preserving stereochemical integrity. The acyl triazolium intermediate generated under catalytic conditions can be employed as a chiral acylating agent in the desymmetrization of meso-diols.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

N-Heterocyclic carbene-catalyzed oxidations

et al. 2009

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“…3 Carbene catalysis is highly versatile and allows access to acyl anions, 4 homoenolates, 5 enolates, 6 Cannizarro-type reductions, 3 c and oxidations. 7 The majority of NHC catalysis currently involves the 1,2-addition of the carbene to a carbonyl-containing species which then proceeds to produce an acyl anion or homoenolate equivalent. A different mode for these nucleophilic catalysts is a conjugate addition manifold.…”

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confidence: 99%

N-heterocyclic carbene-catalyzed rearrangements of vinyl sulfones

2011

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N-heterocyclic carbenes catalyze the rearrangement of 1,1-bis(arylsulfonyl)ethylene to the corresponding trans-1,2-bis(phenylsulfonyl) under mild conditions. Tandem rearrangement/cycloadditions have been developed to capitalize on this new process and generate highly substituted isoxazolines and additional heterocyclic compounds. Preliminary mechanistic studies support a new conjugate addition/Umpolung process involving the ejection and subsequent unusual re-addition of a sulfinate ion.

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“…[3] Inspired by the biological conversion of pyruvate into acetyl Co-A by a thiamin cofactor, NHC catalysis utilizes the electron lone pair of nitrogen-containing heterocycles (i.e., thiazolium, imidazolium, and triazolium-derived carbenes) to promote a variety of reactions including acyl anion chemistry, [4] homoenolate [5] and enolate [6] equivalents, reductions, [3c] and oxidations. [7] Carbene catalysis is well known for the 1,2-addition of the carbene to a carbonyl group of a substrate, affording an acyl anion or homoenolate equivalent (Scheme 1). A less developed reactivity mode for these Lewis base catalysts is the conjugate addition of an α,β-unsaturated carbonyl-containing compound to generate a reactive enolate intermediate.…”

Section: Introductionmentioning

confidence: 99%