Pyridinium N-ylides Research Articles

Indolizines and pyrrolo[1,2-c]pyrimidines decorated with a pyrimidine and a pyridine unit respectively.

The three possible structural isomers of 4-(pyridyl)pyrimidine were employed for the synthesis of new pyrrolo[1,2-c]pyrimidines and new indolizines, by 1,3-dipolar cycloaddition reaction of their corresponding N-ylides generated in situ from their corresponding cycloimmonium bromides. In the case of 4-(3-pyridyl)pyrimidine and 4-(4-pyridyl)pyrimidine the quaternization reactions occur as expected at the pyridine nitrogen atom leading to pyridinium bromides and consequently to new indolizines via the corresponding pyridinium N-ylides. However, in the case of 4-(2-pyridyl)pyrimidine the steric hindrance directs the reaction to the pyrimidinium N-ylides and, subsequently, to the formation of the pyrrolo[1,2-c]pyrimidines. The new pyrrolo[1,2-c]pyrimidines and the new indolizines were structurally characterized through NMR spectroscopy. The X-ray structures of two of the starting materials, 4-(2-pyridyl)pyrimidine and 4-(4-pyridyl)pyrimidine, are also reported.

Reactions of Pyridinium N-Ylides and Their Related Pyridinium Salts

Reactions of Pyridinium N-Ylides and Their Related Pyridinium Salts

Preparation of New Nitrogen‐Bridged Heterocycles Using Pyridinium N‐Ylides and Pyridinium Salts

AbstractFor Abstract see ChemInform Abstract in Full Text.

ピリジニウムＮ‐イリドあるいはピリジニウム塩を利用する新しい橋頭窒素複素環化合物の合成

It is well known that pyridinium N-ylides and their relating pyridinium salts are very useful precursors for the syntheses of some nitrogen-bridged heterocycles, especially, indolizine and pyrazolo [1, 5-a] pyridine. The conventional preparative methods such as the 1, 3-dipolar cycloaddition and the 1, 5-dipolar cyclization of pyridinium N-ylides, and Tschitschibabin reactions of 1-acylmethyl-2-alkyl or aralkylpyridinium salts are convenient to the syntheses of their derivatives, but the compounds obtained thus are helpless for further transformation to fused indolizines and pyrazolo [1, 5-a] pyridines except a few examples. This article describes novel preparative methods for some functionalized indolizines and pyrazolo [1, 5-a] pyridines and their transformation to new fused heterocycles using their functionality.

Synthesis of indolizine derivatives by the reaction of 2-(2′-pyridyl)-pyridinium ylides with ethylenic dipolarophiles

The reaction of 2-(2′-pyridyl)-pyridinium N-ylides with substituted ethylenes such as acrylonitrile and ethyl acrylate gave the corresponding tetrahydroindolizine derivatives in high yields. Tetrahydroindolizine derivatives were dehydrogenated by treating with tetrapyridinecobalt(II) bichromate [CoPy 4(HCrO 4) 2] to give aromatic indolizines bearing cyano, aroyl, 2′-pyridyl, ester group at the different positions. Seventeen new indolizine derivatives were prepared.

Preparation of 1-trifluoroacetyl indolizines and their derivatives via the cycloaddition of pyridinium N-ylides with 4-4-ethoxy1-1,1,1-trifluorobut-3-en-one

Under basic reaction conditions pyridinium or isoquinolinium N-ylides (C 5H 5N + CH 2YBr − or C 9H 7N +CH 2YBr −, Y : CO 2R, CN, PhCO) reacted readily with 4-ethoxyl-1,1,1-trifluorobut-3-en-2-one to give the corresponding 1-trifluoroacetyl substituted indolizines or pyrrolo-[1,2-a]isoquinolines. The molecular structure of 1-trifluoromethyl-3-methoxyl-pyrrolo-[1,2-a]isoquinoline is presented.

Synthesis of 5-(2-Phenylethenyl)indolizines by Selective Intermolecular 1,3-Dipolar Cycloaddition of 2-(2-Phenylethenyl)pyridinium N-Ylide with Alkenes Promoted by Tetrakis-pyridine Cobalt(II) Dichromate

Intermolecular 1,3-dipolar cycloadditions of 2-(2-phenylethenyl)pyridinium N-ylides (3a–d) with electron-deficient alkenes (5a–d) were carried out selectively in the presence of tetrakis-pyridine cobalt(II) dichromate to yield 5-(2-phenylethenyl)indolizines (6a–j) in moderate yields (48–63%).

Synthesis of 5-(2-Phenylethenyl)indolizines by Selective Intermolecular 1,3-Dipolar Cycloaddition of 2-(2-Phenylethenyl)pyridinium N-Ylide with Alkenes Promoted by Tetrakis-pyridine Cobalt(ii) Dichromate

Intermolecular 1,3-dipolar cycloadditions of 2-(2-phenylethenyl)pyridinium N-ylides (3a–d) with electron-deficient alkenes (5a–d) were carried out selectively in the presence of tetrakis-pyridine cobalt(II) dichromate to yield 5-(2-phenylethenyl)indolizines (6a–j) in moderate yields (48–63%).

Preparation of indolizine-3-carboxamides and indolizine-3-carbonitriles by 1,3-dipolar cycloaddition of N-(cyanomethyl)pyridinium ylides to alkenes in the presence of tetrakispyridinecobalt(II) dichromate or manganese(IV) oxide

Two selective procedures for the synthesis of potentially important agrochemicals, indolizine-3-carboxamides (6) and indolizine-3-carbonitriles (7), were developed. In the presence of tetrakispyridinecobalt(II) dichromate (TPCD), compounds 6 are readily synthesized by a one-pot reaction sequence which consists of a 1,3-dipolar cycloaddition of pyridinium N-ylides to alkenes, followed by an aromatization and a regiospecific hydration reaction. When MnO2 instead of TPCD was used in the 1,3-dipolar addition reaction, the nitrile group of the indolizine product was not hydrated and compounds 7 were obtained as final products. Both procedures utilize convenient conditions and inexpensive reagents, and give products in good to high yields.

2-Alkoxycarbonylcycloimmonium ylides, efficient 1,4-dipole equivalents in the synthesis of new conjugated betaines.

Several heterocyclic mesomeric betaines containing the bicyclic systems pyridol[1,2-a]pyrazine and pyrido [2,1-f][1,2,4]triazine have been prepared by reaction of 2-alkoxycarbonyl pyridinium N-ylides with phenyl isocyanate and isothiocyanate.

A facile one-step synthesis of aromatic indolizines by 1,3-dipolar cycloaddition of pyridinium and related heteroaromatic ylides with alkenes in the presence of TPCD [Copy4(HCrO4)2

A facile and general one-step method is presented for the synthesis of aromatic indolizine compounds 3a–n in moderate to high yields (53–99%) by reaction of the pyridinium N-ylides 1a–e, the quinolinium N-ylide 1f and the isoquinolinium N-ylide 1g with various olefinic dipolarophiles, such as acrylonitrile 2a, methyl acrylate 2b, acrylamide 2c, diethyl maleate 2d and methyl crotonate 2e, respectively, in the presence of a new oxidant TPCD [Copy4(HCrO4)2, tetrapyridinecobalt(II) dichromate] at 90 °C for 2 h in DMF.

ChemInform Abstract: A New Synthesis of Imidazo(1,2‐a)pyridine and Imidazo(2,1‐a)isoquinoline Derivatives.

AbstractN‐Bis(methylthio)methylene‐p‐toluenesulfonamide (IV) is prepared from tosylamide (II), carbon disulfide (I), and dimethyl sulfate (III).

Reaction of 2-bis(methylthio)methyleneindan-1,3-dione with N-ylides and S-ylides.

The reaction of 1 with pyridinium N-ylides (2a, R=H ; 2b, R=3-CH3 ; 2c, R=2-CH3 ; and 2d, R=2-NH2) gave the corresponding stable pyridinium N-allylide compounds (3a and 3b), 2-(2-indanyl) indolizine (4), and 3-(2-indanylidenyl) methylimidazo [1, 2-a] pyridine (5) in good yields. A fused thiabenzene oxide, 2-methyl-4-methylthio-5-oxo-5H-indeno [1, 2-c] thiapyran 2-oxide (8), was synthesized by the reaction of 1 with trimethylsulfoxonium iodide under similar conditions. An azathiabenzene oxide, 2-methyl-4-methylthio-5-oxo-5H-indeno [2, 1-d] [1, 2] thiazine 2-oxide (11), was also synthesized from 2-(1-dimethylsulfoximino-1-methylthio) methyleneindan-1, 3-dione (10), which was prepared from 1 and sulfoximine.

Photochemistry as a Tool in Heterocyclic Synthesis: Form Pyridinium N-Ylides to Diazepines and Beyond

Photochemistry as a Tool in Heterocyclic Synthesis: Form Pyridinium N-Ylides to Diazepines and Beyond

Photochemistry as a Tool in Heterocyclic Synthesis. From Pyridinium N-Ylides to Diazepines and Beyond

Photochemistry as a Tool in Heterocyclic Synthesis. From Pyridinium N-Ylides to Diazepines and Beyond

Reaction of pyridinium N-ylides with ketenethioacetal derivatives.

Reaction of the pyridinium N-ylides with ketenethioacetals in the presence of triethylamine or potassium carbonate as a base in ethanol or dimethylformamide gave the pyridinium N-allylides which were readily cyclized to afford the indolizine derivatives.