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, 2011, Pages 143–180Edited By Gordon Gribble and John A. Joule
Chapter 5.2 – Five-Membered Ring Systems: Pyrroles and Benzo Analogs, , , , * St. Norbert College, De Pere, WI, 54115, USA** Hobart and William Smith Colleges, Geneva, NY, 14456, USAThis chapter presents the synthesis and chemistry of pyrroles, indoles, and fused-ring systems. Pyrroles and especially indoles continue to draw a lot of attention from the scientific community because of their prevalence in natural products and wide range of biological and materials science applications. Multi-component reactions leading to pyrroles and pyrrole syntheses by transformation of other heterocycles are described in the chapter. Intramolecular &type a& approaches to pyrroles mainly fall into three general categories: (1) the cyclocondensation reactions of γ- (2) the metal-mediated 5-endo cyclizations of
and (3) the metal-mediated 5-exo cyclizations of γ-aminoalkynes. Two established methods for preparing pyrroles via &type c& processes include the intramolecular cyclization of enaminones and the ring-closing metathesis (RCM) of 4-aza-1,6-dienes (and subsequent oxidation). Several established pyrrole name reactions involve &type ac& cyclizations including Knorr (α-aminocarbonyls + 1,3-dicarbonyls), Trofimov (oximes + alkynes), and Piloty&Robinson (hydrazines + aldehydes/ketones).
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S. CICCHI, S. CREA, A. GOTI andA. BRANDIDOI:&10.1002/chin.
ChemInform page no, Author InformationDip. Chim. Org. &Ugo Schiff&, Univ. Firenze, I-50121 Firenze, ItalyPublication HistoryIssue online: 3 AUG 2010Version of Record online: 3 AUG 2010
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stereochemistry (general, optical resolution);pyrrole derivativesChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a &Full Text& option. The original article is trackable via the &References& option.Seven &-amino alcohols are prepared by a convenient method based on 1,3-dipolar cycloaddition of the nitrone (I) to olefins. Among them the alcohols (VI) and (VIIa) are best catalysts in zinc mediated alkylation of benzaldehyde. However, only modest enantioselectivity is observed.&
S. CICCHI, S. CREA, A. GOTI, A. BRANDI, Synthesis of New Enantiopure &-Amino Alcohols: Their Use as Catalysts in the Alkylation of Benzaldehyde by Diethylzinc., Tetrahedron: Asymmetry, 1997, 8, 293-301. ,,Leimgruber-Batcho_indole_synthesis
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|Leimgruber-Batcho_indole_synthesis
The Leimgruber-Batcho indole synthesis is a series of
that produce
from o-nitro 1.[1][2][3]
The first step is the formation of an
2 using N,N-dimethylformamide dimethyl acetal and .[4]
The desired indole 3 is then formed in a second step by
cyclisation.
In the above scheme, the reductive cyclisation is effected by
and , , [5], or
in [6] are also effective .
In the initial enamine formation,
(a gas) is displaced by
from the dimethylformamide dimethylacetal, producing a more reactive reagent.
The mildly acidic hydrogens of the methyl group in the nitrotoluene can be deprotonated under the basic conditions, and the resultant
attacks to produce the
shown, with loss of .
The sequence can be also be performed without the pyrrolidine, via the N,N-dimethyl enamine, though reaction times may be much longer in some cases.
In the second step the
is reduced to -NH2 using
catalyst, followed by cyclisation then
of the pyrrolidine.
The hydrogen is often generated in situ by the spontaneous decomposition of
hydrate to
in the presence of the nickel.
The reaction is a good example of a reaction that was widely used in industry before any procedures were published in the mainstream scientific literature.
Many indoles are , so a good indole synthesis is important for the
The process has become a popular alternative to the
because many starting
commercially available or easily made.
In addition, the reactions proceed in high
under mild conditions.
The intermediate enamines are electronically related to , having an
nitro group
to an electron-donating group.
The extended conjugation means that these compounds are usually an intense red colour.
Dinitrostyrene reductive cyclization
The reductive cyclization of dinitrostyrenes (1) has proven itself effective when other more common methods have failed.[7]
Most of the standard reduction methods listed above are successful with this reaction.
& Batcho, A. D.; Leimgruber, W. U.S. Patent 3,732,245& & U.S. Patent 3,976,639&
& Batcho, A. D.; Leimgruber, W.
1985, 63, 214-220. (Article)
& Clark, R. D.; Repke, D. B. Heterocycles 1984, 22, 195-221. (Review)
& Maehr, H.; Smallheer, J. M.
1981, 46, 1753. (doi:10.1021/jo)
& Garcia, E. E.; Fryer, R. I. J. Heterocycl. Chem. 1974, 11, 219.
& Ponticello, G. S.; Baldwin, J. J.
1979, 44, 4003. (doi:10.1021/jo)
& Chen, B.-C.; Hynes, Jr., J.; Randit, C. R.; Zhao, R.; Skoumbourdis, A. P.; Wu, H.; Sundeen, J. E.; Leftheris, K. Heterocycles 2001, 55, 951.
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M. AYOUB, G. CHASSAING, A. LOFFET andS. LAVIELLEDOI:&10.1002/chin.
ChemInform page no, Author InformationLab. Chim. Org. Biol., CNRS, Univ. P. et M. Curie, F-75005 Paris, Fr.Publication HistoryIssue online: 17 AUG 2010Version of Record online: 17 AUG 2010
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amino acids,stereochemistry (general, optical resolution);alkylation, arylation, dealkylation, dearylation, C-acylation, olefinationAbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a &Full Text& option. The original article is trackable via the &References& option.This page uses JavaScript to progressively load the article content as a user scrolls.
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, 29 October 2007, Pages 1–13
Conformational studies of 3-aminomethylene-2,4-pentanedione using vibrational and NMR spectra, and ab initio calculations, , , , , , , a Department of Physical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, SK-81237 Bratislava, Slovakiab Department of Organic Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, SK-81237 Bratislava, Slovakiac Central Laboratories, Faculty of Chemical and Food Technology, Slovak University of Technology, SK-81237 Bratislava, Slovakiad Institute of Analytical Chemistry, Technical University Dresden, D-01062 Dresden, GermanyThe IR, Raman and NMR spectra of 3-aminomethylene-2,4-pentanedione (AMP) H2NCHC(COCH3)2 were measured. According to the NMR spectra in chloroform and more polar DMSO at room temperature, the sample exists as single entity. On the other hand vibrational spectra revealed that in less polar solutions AMP exists as two conformers with EZ or ZZ orientation of acetyl groups whereas in more polar solvent only one EZ conformer is observed. Such interpretation was confirmed also by the temperature-dependent measurements of IR spectra in chloroform. The observed IR and Raman bands were compared with harmonic vibrational frequencies, calculated using ab initio MP2 and B3LYP density functional methods in 6-31G&& basis set, and assigned on the basis of potential energy distribution.In addition, the geometries and relative energies of possible conformers of AMP were also evaluated at the same levels of theory and compared with the data from X-ray analysis which revealed that AMP exists in solid state as EZ conformer. The influence of environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using PCM, IPCM and ONSAGER models.KeywordsVibrational and NMR spectra; Conformational analysis; Push&pull enamines; Ab initio calculations; Solvent effect calculations
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