- Microwave-assisted nafion-H catalyzed friedel-crafts type reaction of aromatic aldehydes with arenes: Synthesis of triarylmethanes
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A new solid acid Nafion-H, a perfluorinated sulfonic acid resin, catalyzed microwave-assisted synthesis of triarylmethanes is described. Various benzaldehydes react readily with arenes to provide the corresponding triarylmethanes in good to excellent yields. The reactions were carried out under solvent free conditions under microwave irradiation in a pressure vessel. The solvent free microwave irradiation methods appears to be an environmentally friendly synthetic protocol providing products in significantly shorter reaction times over traditional heating methods carried out in a pressure tube.
- Prakash, Surya G. K.,Fogassy, Gabriella,Olah, George A.
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experimental part
p. 155 - 159
(2011/01/04)
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- BF3-H2O catalyzed hydroxyalkylation of aromatics with aromatic aldehydes and dicarboxaldehydes: Efficient synthesis of triarylmethanes, diarylmethylbenzaldehydes, and anthracene derivatives
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(Figure Presented) BF3-monohydrate is found to be an efficient and strong acid catalyst as well as an effective protosolvating medium suitable for the hydroxyalkylation of arenes with aromatic aldehydes. This reaction has been extended to aromatic dialdehydes, such as terephthalic dicarboxaldehyde and isoterephthalic dicarboxaldehyde, for the efficient synthesis of diarylmethylbenzaldehydes, which are useful synthons for various organic transformations. Further, successful one step convergent synthesis of various synthetically useful anthracene derivatives from phthalaldehyde was also achieved. BF3-H2O is less expensive and acts as an efficient substitute for nonoxidizing strong protic acids/superacids.
- Prakash, G. K. Surya,Panja, Chiradeep,Shakhmin, Anton,Shah, Eric,Mathew, Thomas,Olah, George A.
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supporting information; experimental part
p. 8659 - 8668
(2009/12/30)
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- Synthesis of (p-Nitroaryl)diarylmethanes via vicarious nucleophilic substitution of hydrogen
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(p-Nitroaryl)diarylmethanes are readily prepared via vicariousm nucleophilic substitution of hydrogen in nitroarenes with carbanions of diarylmethyl p-chlorophenyl sulfide. These carbanions are efficient reagents for introduction of diarylmethyl substituents in the para position of nitroarenes via the VNS reaction. The reaction does not proceed ortho to the nitro group due to steric hindrances on the addition step.
- Makosza,Surowiec,Voskresensky
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p. 1237 - 1240
(2007/10/03)
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- Palladium-catalyzed coupling reaction of 4-alkylnitrobenzenes with aryl bromides at their benzylic position
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4-Alkylnitrobenzenes effectively undergo coupling with aryl bromides at their benzylic position in the presence of a palladium catalyst and a base to give the corresponding mono- and/or di-arylated products in good yields.
- Inoh, Jun-Ichi,Satoh, Tetsuya,Pivsa-Art, Sommai,Miura, Masahiro,Nomura, Masakatsu
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p. 4673 - 4676
(2007/10/03)
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- First General Synthesis of (p-Nitroaryl)diarylmethanes via Vicarious Nucleophilic Substitution of Hydrogen
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A general regiospecific method for the synthesis of (p-nitroaryl)diarylmethanes has been developed starting from diarylmethanols and 2- and/or 3-substituted nitrobenzenes. This utilizes the quantitative condensation between benzotriazole and diarylmethanols under acidic catalysis and in the presence of perfluorocarbon fluids, followed by vicarious nucleophilic substitution of the resulting diarylmethylbenzotriazoles upon nitrobenzenes in moderate to high yield, Oxidative nucleophilic substitution of hydrogen is observed as a side process. These vicarious nucleophilic substitutions complement Friedel-Crafts reactions for the synthesis of triarylmethanes.
- Katritzky, Alan R.,Toader, Dorin
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p. 4137 - 4141
(2007/10/03)
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- Superacid-catalyzed reaction of substituted benzaldehydes with benzene
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Benzaldehydes bearing an electron-withdrawing group reacted with 2 equiv of benzene in the presence of a superacid, trifluoromethanesulfonic acid, to give substituted triphenylmethane in good yields. On the other hand, benzaldehydes bearing an electron-donating or a neutral group reacted under the similar conditions to give unsubstituted diphenylmethane and triphenylmethanol, together with substituted benzene. We propose a new mechanism of this reaction, which involves transalkylation as the key step.
- Saito, Shinichi,Ohwada, Tomohiko,Shudo, Koichi
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p. 8089 - 8093
(2007/10/03)
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- Phenylazo-Substituted Triphenylmethylium Systems
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Triphenylmethanols (or their ethers) bearing phenylazo groups react with trifluoroacetic acid to give deeply colored solutions of the tritylium ions 7(+) - 9(+), (RC6H4N=NC6H4)nC(+)(C6H5)3-n (R = H, Me, Cl, NO2, MeO, H2N, Me2N), whose long wavelengths VIS absorptions and lowfield 1H-NMR signals are consistent with the existence of through-conjugated ?-electron systems.After addition of trifluoromethanesulfonic acid significant hypsochromic shifts of the VIS bands as well as additional proton deshieldings in the 1H-NMR spectrum are observed, which are in accordance with the formation of proximally azo-protonated phenylazotritylium ions 7(+)*H(+), 8(+)*2H(+), and 9(+)*3H(+), (RC6H4N=N(+)H-C6H4)nC(+)(C6H5)3-n.Fully analogous acid-strength-dependent ionisation/protonation reactions result for the overall p-substituted ions 17(+), 18(+), (RC6H4N=NC6H4)C(+)(C6H4R')2 (R,R' = Me, MeO, Me2N), as well as for the azobistritylium system 10(2+), (C6H5)2C(+)C6H4N=NC6H4C(+)(C6H5)2, and its azoxy derivative 11(2+).The linearly extended bis- and trisazo systems 19(+), 22(+), MeC6H4N=N(C6H4N=N)1,2C6H4C(+)(C6H5)2 and the (phenylazo)styryl system 20(+), MeC6H4N=NC6H4CH=CHC6H4C(+)(C6H5)2 in trifluoroacetic acid do not show any significant color changes relativ to the corresponding monofunctional parent types.In trifluoromethanesulfonic acid, however, compounds 19(+), 22(+) exhibit the usual bathochromic shifts of the longest wavelenght VIS absorption accompanying the increasing protonation of the polyazo system.In the case of the tritylium ions containing azomethine bridges, 24(+), only for the methoxy derivative 24b(+) indications for the existence of the conjugatively extended tritylium system (MeOC6H4N=CHC6H4)C(+)(C6H5)2 are found.The amide derivatives 26(+)-29(+), on the other hand, presents no clues for the existence of through-conjugated systems of the kind ArC(OH)=NC6H4C(+)Ar2 and ArN=C(OH)C6H4C(+)Ar2, respectively.
- Hellwinkel, Dieter,Fritsch, Helmut
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p. 2207 - 2226
(2007/10/02)
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