Showing papers by "J. Carlos Menéndez published in 2007"
TL;DR: In this article, it was shown that CAN catalyzes the three-component domino reaction between aromatic amines, α, β-unsaturated aldehydes, and ethyl acetoacetate, providing an efficient new entry into 1,4-dihydropyridines.
83 citations
TL;DR: The CAN-catalyzed reaction between anilines and vinyl ethers at room temperature provides a convenient and efficient access to 4-alkoxy-2-methyl-1,2,3,4-tetrahydroquinolines as discussed by the authors.
56 citations
TL;DR: This constitutes the first example of an alpha,beta-unsaturated dimethylhydrazone behaving as a dienophile in a hetero Diels-Alder reaction and the first vinylogous aza-Povarov reaction.
Abstract: The reaction between aromatic imines and methacrolein dimethylhydrazone in the presence of 10% indium trichloride affords in good to excellent yields biologically and synthetically relevant 1,2,3,4-tetrahydroquinolines bearing a hydrazone function at C-4 in a one-pot process that involves the formation of two C–C bonds and the stereoselective generation of two stereocenters, one of them quaternary, and this constitutes the first example of an α,β-unsaturated dimethylhydrazone behaving as a dienophile in a hetero Diels–Alder reaction and the first vinylogous aza-Povarov reaction.
49 citations
01 Jan 2007
TL;DR: The welwitindolinones are a group of structurally unique metabolites isolated from cyanobacteria, containing 3,4-bridged or spiro cyclobutaneoxindole moieties as discussed by the authors.
Abstract: Marine cyanobacteria are a prolific source of bioactive natural products The welwitindolinones are a group of structurally unique metabolites isolated from cyanobacteria, containing 3,4-bridged or spiro cyclobutaneoxindole moieties Due to their challenging structures and their broad spectrum of biological activities, these compounds have attracted the attention of synthetic chemists for some time, although so far their complexity has prevented the completion of total syntheses for most of these natural products This chapter is devoted to a discussion of the current knowledge about the occurrence, biological properties, biosynthesis and synthetic approaches to the welwitindolinones
20 citations
TL;DR: In this paper, it was shown that CAN catalyzes the three-component domino reaction between aromatic amines, α, β-unsaturated aldehydes, and ethyl acetoacetate, providing an efficient new entry into 1,4-dihydropyridines.
Abstract: Cerium ammonium nitrate (CAN) catalyzed the three-component domino reaction between aromatic amines, α,β-unsaturated aldehydes, and ethyl acetoacetate, providing an efficient new entry into 1,4-dihydropyridines. This new reaction requires very mild reaction conditions, has water as the only side product and is complementary to the classical Hantzsch synthesis in that it is well suited to the preparation of N-aryl-5,6-unsubstituted dihydropyridines. Experiments in the presence of a radical trap suggest that a one-electron oxidative mechanism can be excluded and that CAN acts as a Lewis acid.
10 citations
TL;DR: Several 3,4 disubstituted indole building blocks were synthesized, containing a one-carbon functional group at C-4 and a three-carbon chain bearing at least one functional group.
Abstract: Several 3,4-disubstituted indole building blocks were synthesized, containing a one-carbon functional group at C-4 and a three-carbon chain bearing at least one functional group. A C-4 functionalized indole derivative was prepared by application of the Leimgruber-Batcho reaction. Several three-carbon chains were subsequently installed at the indole C-3 position. In the first strategy employed, a Mannich reaction was followed by the creation of a C-C bond by phosphine-induced generation of a 3-methyleneindolenine species, which was trapped by diethyl malonate. Alternatively, a Vilsmeier formylation at C-3 was followed by Knoevenagel or Wittig reactions or by treatment with ethyl diazoacetate in the presence of a Lewis acid. Direct introduction of the three-carbon chain at C-3 using a Lewis acid-catalyzed Michael reaction was also achieved. Further functionalization of the benzylic position attached to C-4 by attachment of a nitro group was carried out, but preparation of a tricyclic welwistatin fragment by intramolecular nitroalkane acylation or in- tramolecular Henry reactions was not possible.
10 citations
TL;DR: The reaction proceeds smoothly at room temperature in short reaction times and gives β-enaminones in good to excellent yields as mentioned in this paper, and β-dicarbonyl compounds, including β-ketoesters, β -ketothioesters, and β -diketones.
Abstract: Ceric ammonium nitrate catalyzes the reaction between aromatic or aliphatic primary amines and a variety of β-dicarbonyl compounds, including β-ketoesters, β-ketothioesters and β-diketones. The reaction proceeds smoothly at room temperature in short reaction times and gives β-enaminones in good to excellent yields.
9 citations
TL;DR: Ceric ammonium nitrate catalyzes the reaction between aromatic or aliphatic primary amines and a variety of β-dicarbonyl compounds, including β-ketoesters,β-ketothioesters andβ-diketones, and gives β-enaminones in good to excellent yields.
Abstract: Ceric ammonium nitrate catalyzes the reaction between aromatic or aliphatic primary amines and a variety of β-dicarbonyl compounds, including β-ketoesters, β-ketothioesters and β-diketones. The reaction proceeds smoothly at room temperature in short reaction times and gives β-enaminones in good to excellent yields.
6 citations
TL;DR: The CAN-catalyzed reaction between anilines and vinyl ethers at room temperature provides a convenient and efficient access to 4-alkoxy-2-methyl-1,2,3,4-tetrahydroquinolines.
Abstract: The CAN-catalyzed reaction between anilines and vinyl ethers at room temperature provides a convenient and efficient access to 4-alkoxy-2-methyl-1,2,3,4-tetrahydroquinolines. This reaction is stereoselective, favouring a cis arrangement for the alkoxy and methyl groups, and involves a three-component process that leaves a molecule of alcohol as the only side product. 2-Methylquinoline derivatives were efficiently prepared from 4-alkoxy-2-methyl-1,2,3,4-tetrahydroquinolines by Pd–C-promoted dehydrogenation.
5 citations
TL;DR: The CAN-catalyzed reaction between anilines, cinnamaldehyde and vinyl ethers affords 2-styryl-1,2,3,4-tetrahydroquinolines as discussed by the authors.
Abstract: The CAN-catalyzed reaction between anilines, cinnamaldehyde and vinyl ethers affords 2-styryl-1,2,3,4-tetrahydroquinolines. In the case of noncyclic vinyl ethers, these reactions are completely stereoselective and furnish exclusively the diastereomer with a cis relationship between the styryl and alkoxy groups.
4 citations
TL;DR: In this article, the effect of different chemically modified cyclodextrins (CDs) added to the aqueous solutions of these reagents was studied in water and in buffered annealing solutions at pH 4.5 and 8.8.
Abstract: Carbazole-9-carbonyl chloride (C9CC) and 9-carbazolylacetic acid (9CAA) were selected as model fluorescent reagents. The effect of different chemically modified cyclodextrins (CDs) added to the aqueous solutions of these reagents was studied in water and in buffered aqueous solutions at pH 4.5 and 8.8. The CDs employed were 2-hydroxypropyl-β-cyclodextrin (HP-βCD), 2,3-di-O-methyl-β-cyclodextrin (DM-βCD) and 2,3,6-tri-O-methyl-β-cyclodextrin (TM-βCD). The inclusion of these reagents inside the cavities of the CDs was verified and this process can affect the derivatization reaction because CDs can modify the reactivity of the guest molecules. The basic conditions necessary for the derivatization reaction between C9CC and amines lead to the formation of carbazole anion through hydrolysis followed by decarboxylation. In the presence of CDs, the hydrolysis-decarboxylation of carbazole-9-carbonyl chloride is faster than in buffered aqueous homogeneous solutions. The behaviour observed for these reagents in aqueous solutions of CDs was compared to the one observed in basic ethanolic solutions. These changes are particularly noticeable in the case of 2,3-di-O-methyl-β-CD and 2-hydroxypropyl-β-CD. The characteristics of the fluorescent reagents are compared to carbazole and 9-methylcarbazole as model compounds.
TL;DR: In this article, the reaction between aromatic imines and methacrolein dimethylhydrazone in the presence of 10% indium trichloride affords good to excellent yields biologically and synthetically relevant 1,2,3,4-tetrahydroquinolines bearing a hydrazone function at C-4 in a one-pot process.
Abstract: The reaction between aromatic imines and methacrolein dimethylhydrazone in the presence of 10% indium trichloride affords in good to excellent yields biologically and synthetically relevant 1,2,3,4-tetrahydroquinolines bearing a hydrazone function at C-4 in a one-pot process that involves the formation of two C–C bonds and the stereoselective generation of two stereocenters, one of them quaternary, and this constitutes the first example of an α,β-unsaturated dimethylhydrazone behaving as a dienophile in a hetero Diels–Alder reaction and the first vinylogous aza-Povarov reaction.
TL;DR: Microwave irradiation leads to a considerable improvement of cyclocondensation between anthranilic acid and lactim ethers derived from piperazine-2,5-diones in terms of reaction times, yields, and stereocenter integrity as mentioned in this paper.
Abstract: Microwave irradiation leads to a considerable improvement of the cyclocondensation between anthranilic acid and lactim ethers derived from piperazine-2,5-diones in terms of reaction times, yields, and stereocenter integrity. This reaction has been used to prepare some derivatives of the pyrazino[2,1- B]quinazoline-3,6-dione system present in many quinazoline alkaloids. It could also be applied to the synthesis of compounds containing the complete hexacyclic ring system of the anti-MDR natural product N-acetyl-ardeemin, and other comprising the pentacyclic framework of circumdatin E. The microwave-assisted reaction was also much better than the thermal one when applied to a bis-lactim ether, leading to the corresponding pentacyclic pyrazino[2,1- B:5,4- B′]diquinazoline-8,16-dione in excellent yield.
TL;DR: In this article, an ortho-directed method was proposed for 6-pivaloylamino-4-methyl-5,8-dimethoxy carbostyril derivatives, which allowed the preparation of de- rivatives containing alkyl chains or functional groups at the C-7 position.
Abstract: An ortho-directed lithiation strategy starting from 2-ami- no-1,4-dimethoxybenzene derivatives allowed the efficient prepa- ration of 2-amino-3-alkylbenzoquinone derivatives. This method was also successful in the case of 6-pivaloylamino-4-methyl-5,8- dimethoxycarbostyril derivatives, in spite of the fact that two other modes of lithiation are possible, and allowed the preparation of de- rivatives containing alkyl chains or functional groups at the highly hindered C-7 position. A reaction starting from 4-methyl-5,8- dimethoxy-2-pivaloyloxyquinoline was regioselectively directed to the C-4 methyl group.
TL;DR: The CAN-catalyzed reaction between anilines, cinnamaldehyde and vinyl ethers affords 2-styryl-1,2,3,4-tetrahydroquinolines.
Abstract: The CAN-catalyzed reaction between anilines, cinnamaldehyde and vinyl ethers affords 2-styryl-1,2,3,4-tetrahydroquinolines. In the case of noncyclic vinyl ethers, these reactions are completely stereoselective and furnish exclusively the diastereomer with a cis relationship between the styryl and alkoxy groups.