Synthesis of five-membered aromatic heterocycles

Gilchrist, T. L.

doi:10.1039/co9940100205

Cited by 22 publications

(6 citation statements)

References 87 publications

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“…Single crystals suitable for X-ray diffraction were grown after storage for several days at 4 8C. 1 [a] Very small amounts of the iodides 3 and 4 were detected (< 5 %).…”

Section: Methodsmentioning

confidence: 99%

“…This compound could result from the release of LiTMP from the expected lithium-zinc mixed intermediate A (see Scheme 1). 1 H and 13 C NMR analysis seem to show that the complex 5 is also the main species in solution.…”

Section: Wwwchemeurjorgmentioning

confidence: 96%

“…Substituted pyrroles are structural units present in many natural products and pharmaceutical synthetic intermediates. [1] Among the methods used to functionalize pyrroles, [1] metalation reactions with lithium bases have been devel-oped. [2] These methods often require low temperatures and cannot be used when reactive functional groups are present.…”

Section: Introductionmentioning

confidence: 99%

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Ligand‐Activated Lithium‐Mediated Zincation of N‐Phenylpyrrole

Seggio

Lannou

Chevallier

et al. 2007

Chemistry A European J

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Metalation of N-phenylpyrrole by using an in situ mixture of ZnCl(2)TMEDA (0.5 equiv; TMEDA=N,N,N',N'-tetramethylethylenediamine) and LiTMP (1.5 equiv; TMP=2,2,6,6-tetramethylpiperidino) was optimized. The reaction carried out at room temperature in THF resulted in incomplete metalation (56 % conversion) and selectivity (mixture of 2-iodo and 2,2'-diiodo derivatives in an 86:14 ratio after trapping with iodine). By using diethyl ether (DEE), toluene, or hexane instead of THF, low conversions of 17, 38, or 23 % were observed, respectively, but the formation of the diiodide was avoided. When hexane was used as solvent, strong lithium-complexing ligands such as [12]crown-4 and N,N'-dimethylpropylideneurea (DMPU) inhibited the reaction whereas more (hemi)labile ligands (TMEDA>THF approximately DME) favored it. This result shows that a temporary accessibility of lithium to interact with the rest of the base and/or the substrate is a prerequisite for an efficient metalation. A 75 % yield of 2-iodo-N-phenylpyrrole was obtained after reaction with the base in the presence of five equivalents of TMEDA for two hours at room temperature, and subsequent trapping with iodine. We were able to successfully replace the spare TMP with a less expensive butyl group.

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“…Single crystals suitable for X-ray diffraction were grown after storage for several days at 4 8C. 1 [a] Very small amounts of the iodides 3 and 4 were detected (< 5 %).…”

Section: Methodsmentioning

confidence: 99%

Section: Wwwchemeurjorgmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Ligand‐Activated Lithium‐Mediated Zincation of N‐Phenylpyrrole

Seggio

Lannou

Chevallier

et al. 2007

Chemistry A European J

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“…The importance of the pyrrole ring system has continued to stimulate a great deal of interest in the development of new methodologies for the synthesis of substituted pyrroles. Several recent reviews on this topic are now available. − We have been concerned with the potential elaboration of a new pyrrole synthesis in which BOC-α-amino aldehydes ( 1 , R 2 = H) or ketones ( 1 , R 2 = CH 3 ) are reacted with the lithium enolates derived from ketones 2 to afford, after protonation, aldol intermediates 3 , which then cyclize to the desired pyrroles 4 under mild acidic conditions (Scheme ) . Although conceptually related to the familiar Knorr pyrrole synthesis, in which α-oximino ketones are reduced to α-amino ketones and then reacted with β-diketones or β-keto esters to afford substituted pyrroles, the present method would offer the advantage of employment of BOC-α-amino aldehydes or ketones 1 that are readily available from a wide variety of amino acids.…”

mentioning

confidence: 99%

A General Synthesis of Pyrroles and Fused Pyrrole Systems from Ketones and Amino Acids

Nagafuji

Cushman

1996

J. Org. Chem.

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The lithium enolates of ketones react with BOC-α-amino aldehydes and BOC-α-amino ketones to afford aldol intermediates that cyclize under acidic conditions to yield pyrroles. The BOC-amino aldehydes and ketones are readily available from α-amino acids. The method allows incorporation of a wide variety of substituents at any of the five atoms of the pyrrole ring and is also suitable for the preparation of fused pyrrole systems.

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“…4‐Hydroxthiazolines ( 81 ), which are in tautomeric equilibrium with the oxothiazolidine form, were prepared by the addition of α‐thioacetic acid to imines (Scheme ) by Diurno et al . and Gilchrist et al …”

Section: Introductionmentioning

confidence: 99%

Short Review on the Synthesis of Thiophene, Pyrazole, and Thiazole Derivatives

Elkanzi

2017

J Chinese Chemical Soc

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The review summarizes the synthesis of different thiophene, pyrazole, and thiazole derivatives by refluxing 9a in ethanol with a catalytic amount of TEA or leaving it in DMF containing potassium carbonate at room temperature overnight to afford the corresponding thiophene derivative 10a. In addition, cyclization of Schiff bases with thioglycollic acid in the presence of a catalytic amount of ZnCl2 yielded novel thiophene derivatives. Condensation of 2‐substituted‐4‐methylythio semi‐carbazides 92 with carbonyl compounds under strong acidic conditions afforded 2‐thiazolines. Also, carboxylic acid reacted with 2‐thioethylamine in the presence of triphenylphosphine and triethylamine to afford 2‐thiazolines 98.

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Synthesis of five-membered aromatic heterocycles

Cited by 22 publications

References 87 publications

Ligand‐Activated Lithium‐Mediated Zincation of N‐Phenylpyrrole

Ligand‐Activated Lithium‐Mediated Zincation of N‐Phenylpyrrole

A General Synthesis of Pyrroles and Fused Pyrrole Systems from Ketones and Amino Acids

Short Review on the Synthesis of Thiophene, Pyrazole, and Thiazole Derivatives

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