Ueber die Constitution des Lophins und verwandter Verbindungen

Radziszewski, Br.

doi:10.1002/cber.18820150207

Cited by 216 publications

(106 citation statements)

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“…Imidazole synthesis from α-diketones has a long history 16 and was initially plagued by low yields and by-products (such as oxazoles). Improvements occurred by the use of acidic conditions, e.g., glacial acetic acid reflux.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of imidazole derivatives from β-lapachone and related compounds using microwave and supported reagents

Silva¹,

Silva²,

Ferreira³

et al. 2008

J. Braz. Chem. Soc.

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Naftoimidazóis inéditos foram preparados por reação, ativada por microondas, entre paraformaldeído, β-lapachona (ou o-quinonas correlatas) e acetato de amônio suportado em montmorilonita k-10, ou em alumina básica. O uso do suporte básico forneceu os melhores rendimentos, superiores a 80%. Isso foi confirmado para a reação com β-lapachona e piperonal.New naphthoimidazoles were prepared by reaction, activated by microwave irradiation, between paraformaldehyde, β-lapachone (or related o-quinones) and ammonium acetate supported on montmorillonite k-10, or on basic alumina. Use of the basic support gave the best results, with yields above 80%. This was confirmed for the reaction with β-lapachone and piperonal.Keywords: imidazole, microwave, basic alumina, lapachone Introduction β-Lapachone (1a) is an ortho-naphthoquinone present in small amounts in trees of the Tabebuia species (Bignoniaceae), commonly called "ipê" or "pau d'arco" in Brazil. In addition, it can be obtained by the isomerization of lapachol, a quinone that is more abundant and more readily extracted from the same sources. The biological activities of these compounds and simple derivatives, have been investigated since the 1940's (anti-malarial 1 ) up to the present (anti-tumor, 2 anti-microbial, 3 anti-inflammatory 4 and anti-parasitic 5 ) and were recently reviewed. 6 The use of β-lapachone and some semi-synthetic derivatives as chemotherapic agents in the treatment of American trypanosomiasis (Chagas disease) has been investigated, 7 and five imidazole derivatives, prepared from this quinone and aromatic aldehydes, have shown expressive action over the tripamastigote form of Trypanosoma cruzi. 8,9 These imidazole derivatives were prepared by conventional methods. 9 As part of an ongoing study into the use of microwave activation and the use of supported reagents, in this case ammonium acetate, we investigated the preparation of the previously unknown simple imidazole derivatives of β-lapachone and related ortho-quinones with formaldehyde.Microwave activation has provided significant improvement on heterocyclic synthesis, 10 including imidazoles, with [11][12][13] or without support, 14,15 with reduction/ elimination of solvents, decreased reaction times and equal or improved yields. Results and DiscussionImidazole synthesis from α-diketones has a long history 16 and was initially plagued by low yields and by-products (such as oxazoles). Improvements occurred by the use of acidic conditions, e.g., glacial acetic acid reflux. 17 The availability of microwave technology for synthetic purposes has allowed the efficient preparation of 2,4,5-trissubstituted and 1,2,4,5-tetrassubstituted imidazoles. Further observed benefits, that were occasionally associated with solid supports such as silica, alumina, clays, amongst others, 11-13 included improved yields, and dramatic reductions in reaction time and quantities of solvent used (AcOH). 14,15 Interestingly, the best supports found in these studies were always the acidic in nature.Based on these findings, th...

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Section: Resultsmentioning

confidence: 99%

Synthesis of imidazole derivatives from β-lapachone and related compounds using microwave and supported reagents

Silva¹,

Silva²,

Ferreira³

et al. 2008

J. Braz. Chem. Soc.

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“…The intermediate 5 further reacts with H2O in the reaction system to obtain 2,4,5-tri(furan-2-yl)-2H-imidazole (Intermediate 6) which quickly rearranges to the imidazoles derivatives I. Currently, our experimental support for this proposed mechanism comes from the finding that the imidazole I and small amounts of II and III are obtained, along with intermediate 5 is traced by GC-MS. For the action of ammonia on (aryl-or alky-)ethane-1,2-diketone in synthesizing imidazole derivatives, both Fang et al [4] and Radziszewski [12] thought that the reactions began with the conversion of aldehyde to C-pyridin-2-yl-methanediamine or C-phenylmethanediamine, which condensed with 2,2'-pyridil or benzil to form corresponding 2H-imidazole and then rearranged to the product. However, seen from our result, during the formation of imidazole derivatives the furil was further attacked not by C-furan-methanediamine but by 1,2-di(furan-2-yl)ethane-1,2-diimine to obtain an intermediate 4, which in turn dehydrated, cyclized to afford imidazole derivatives I.…”

Section: Methodsmentioning

confidence: 99%

“…It was mainly used to synthesize imidazole derivatives from 1,2-diketone and appropriate aldehydes [1][2][3][4][5][6][7][8][9][10][11]. The first is Radziszewski's classic synthesis from benzil(1,2-diphenylethane-1,2-dione), benzaldehyde and ammonia in 1882 [12]. The main product 2,4,5-triphenylglyoxaline was confirmed as the structure for lophine.…”

Section: Introductionmentioning

confidence: 99%

Research on the reaction of furil with ammonium acetate

Wang

Chen

et al. 2011

Eur. J. Chem.

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KEYWORDSThe direct reaction of furil with ammonium acetate in refluxing glacial acetic acid under the absence of appropriate aldehydes was systematically studied. The principal product with furan rings and imidazole ring 2,4,5-tri(furan-2-yl)-1H-imidazole (I) was obtained in moderate yield, and two new byproducts containing furan rings were successfully purified by C18 reversed phase column. All compounds were characterized by elemental analysis, MS, IR, 1 H and 13 C NMR spectroscopy. The structure of I was further confirmed by the 13 C-1 H COSY spectroscopy. The putative reaction mechanism via stable 1,2-di(furan-2-yl)ethane-1,2-diimine, furan-2-yl-(2,4,5-tri-furan-2-yl-2H-imidazol-2-yl)-methanone and intermediate 5 traced by GC-MS was proposed.

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“…Already in the late 19 th century there has been an excited discussion about the constitution of lophine and its derivatives [29,30]. Until now, crystal structures of more than 30 derivatives are known, and recently the crystal structure of the parent compound lophine has been reported [37].…”

Section: Crystal Structurementioning

confidence: 99%

Synthesis and Structure of 1-Ethyl-2,4,5-triphenyl-1H-imidazole (Ethyl-Lophine)

Peppel¹,

Köckerling²

2013

Zeitschrift Für Naturforschung B

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Ethyl-Lophine, 1-ethyl-2,4,5-triphenyl-1H-imidazole, C 23 H 20 N 2 , was synthesized as a precursor for large organic cations in ionic liquids using an improved microwave-assisted method. The title compound and a precursor compound were characterized by NMR, IR, and DSC thermal measurements, as well as elemental analyses. The crystal structure of ethyl-lophine was determined by singlecrystal X-ray structure analysis (triclinic, P1, a = 10.1137(3), b = 12.4935(4), c = 14.6351(4)Å, α = 98.182(2) • , β = 90.694(2) • , γ = 102.666(2) • , Z = 4, wR2 = 0.1030 for 611 refined parameters).

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Ueber die Constitution des Lophins und verwandter Verbindungen

Cited by 216 publications

References 0 publications

Synthesis of imidazole derivatives from β-lapachone and related compounds using microwave and supported reagents

Synthesis of imidazole derivatives from β-lapachone and related compounds using microwave and supported reagents

Research on the reaction of furil with ammonium acetate

Synthesis and Structure of 1-Ethyl-2,4,5-triphenyl-1H-imidazole (Ethyl-Lophine)

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