ChemInform Abstract: The Chemistry of Stable Carbenes. Part 2. Benzoin‐Type Condensations of Formaldehyde Catalyzed by Stable Carbenes.

Teles, J. Henrique; Melder, Johann‐Peter; Ebel, Klaus; Schneider, Ralf; Gehrer, Eugen; Harder, W. D.; Brode, Stefan; Enders, Dieter; Raabe, Gerhard

doi:10.1002/chin.199618053

Cited by 2 publications

(3 citation statements)

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“…A normal kinetic deuterium isotope effect for the overall reaction k H /k D ∼ = 3.4 is observed using PhCDO, and a large inverse solvent isotope effect k D /k H ∼ = 5.9 is observed using CD 3 OD, consistent with the mechanism shown in Scheme 47 [321][322][323]. Thiazol-2-ylidenes 79, 1,3,5-triphenyl-1,3,4-triazol-2-ylidene (20) also catalyze the formoin condensation converting formaldehyde into glycoaldehyde (84) (Scheme 48) [324,325]. This reaction is the first step of the formose reaction discovered in 1861 by Butlerow [326] and which generates mixtures of racemic aldoses and ketoses (monosaccharides) by oligomerization of formaldehyde in the presence of Ca(OH) 2 .…”

Section: Benzoin Condensation: Umpolung Of Aldehydessupporting

confidence: 54%

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

et al. 2016

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Catalysis fulfills the promise that high-yielding chemical transformations will require little energy and produce no toxic waste. This message is carried by the study of the evolution of molecular catalysis of some of the most important reactions in organic chemistry. After reviewing the conceptual underpinnings of catalysis, we discuss the applications of different catalysts according to the mechanism of the reactions that they catalyze, including acyl group transfers, nucleophilic additions and substitutions, and C-C bond forming reactions that employ umpolung by nucleophilic additions to C=O and C=C double bonds. We highlight the utility of a broad range of organocatalysts other than compounds based on proline, the cinchona alkaloids and binaphthyls, which have been abundantly reviewed elsewhere. The focus is on organocatalysts, although a few examples employing metal complexes and enzymes are also included due to their significance. Classical Brønsted acids have evolved into electrophilic hands, the fingers of which are hydrogen donors (like enzymes) or other electrophilic moieties. Classical Lewis base catalysts have evolved into tridimensional, chiral nucleophiles that are N-(e.g., tertiary amines), P-(e.g., tertiary phosphines) and C-nucleophiles (e.g., N-heterocyclic carbenes). Many efficient organocatalysts bear electrophilic and nucleophilic moieties that interact simultaneously or not with both the electrophilic and nucleophilic reactants. A detailed understanding of the reaction mechanisms permits the design of better catalysts. Their construction represents a molecular science in itself, suggesting that sooner or later chemists will not only imitate Nature but be able to catalyze a much wider range of reactions with high chemo-, regio-, stereo-and enantioselectivity. Man-made organocatalysts are much smaller, cheaper and more stable than enzymes.

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Section: Benzoin Condensation: Umpolung Of Aldehydessupporting

confidence: 54%

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

et al. 2016

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“…Although carbenes are typically used as ligands for transition metals [11][12][13][14][15], or as nucleophilic organic catalysts [16][17][18][19][20][21][22][23][24][25], these carbene derivatives that contain an (H)CCl3 bound at the carbene C2 position have been found through reductive thermolysis, to give free carbene for reaction with metals [26].…”

Section: Synthetic Discussionmentioning

confidence: 99%

“…The crystal structure has C1-Cl1, C1-Cl2, and C1-Cl3 bond lengths of 1.770(2), 1.7800 (19), and 1.780(2) Å respectively, which are in line with the average C sp 3 -Cl bond length of 1.768(22) Å for interactions of similar nature (mean bond length of 1300 structures found in CSD Release 5.387, May 2017) [27]. In addition, the structure has C1-C2, C2-N1, and C2-N2 bond lengths of 1.576(3), 1.442(2), and 1.450(3) Å, respectively.…”

Section: X-ray Crystallographymentioning

confidence: 99%

1,3-Bis(2,6-diisopropylphenyl)-2-trichloromethylimidazolidine

Stack

Masuda

2017

Molbank

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Abstract:A new chloroform adduct of the N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr) has been prepared via C-H bond activation of the chloroform at the carbene carbon. This redox product was crystallized and was characterized by 1 H and 13 C-NMR spectroscopy, elemental analysis (EA), and single-crystal X-ray diffraction. The 1 H and 13 C-NMR spectroscopic data are in agreement with the crystal structure. Density functional theory (DFT) calculations were performed as a means for comparison to experimental data and the computational results are in agreement with those obtained experimentally.

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ChemInform Abstract: The Chemistry of Stable Carbenes. Part 2. Benzoin‐Type Condensations of Formaldehyde Catalyzed by Stable Carbenes.

Cited by 2 publications

References 1 publication

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

1,3-Bis(2,6-diisopropylphenyl)-2-trichloromethylimidazolidine

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