Reactions Of Pyridinium Ylides Research Articles

Synthesis of 2,3-bifunctional imidazo[1,2-a]pyridines through cycloadditions of pyridinium ylides with N-cyano-4-methyl-N-phenylbenzenesulfonamide

Imidazo[1,2-a]pyridine is recognized as a “drug prejudice” due to its wide applications in medicinal chemistry. In this work, we developed a [3 + 2] cycloadditions/oxidation reaction of pyridinium ylides with N-cyano-4-methyl-N-phenylbenzenesulfonamide for the synthesis of 2,3-bifunctional imidazo[1,2-a]pyridines. The N-cyano-4-methyl-N-phenylbenzenesulfonamide serves as an activated nitrile, exhibiting higher activity than common alkyl or aryl nitrile in the reaction. The strategy features high chemoselectivity, easily accessible materials, and broad substrate scope. The scale-up reaction demonstrated the practicability of this method, and the imidazo[1,2-a]pyridines products could be easily transformed into their derivatives.

ChemInform Abstract: Ultrasound‐Assisted 1,3‐Dipolar Cycloaddition and Cyclopropanation Reactions for the Synthesis of Bis‐Indolizine and Bis‐Cyclopropane Derivatives.

Ultrasound irradiation can promote the 1,3-dipolar cycloaddition reaction of 2-chloropyridinium ylides with 2-benzylidenemalononitrile or 2,2′-(1,4-phenylenebis(methanylylidene))dimalononitrile, to afford the indolizine and bis-indolizine derivatives respectively. While the reaction of pyridinium ylides with 2-benzylidenemalononitrile or 2,2′-(1,4-phenylenebis(methanylylidene))dimalononitrile under ultrasound irradiation provided, in an unusual manner, cyclopropane and bis-cyclopropane derivatives, respectively. These cycloaddition and cyclopropanation reactions were carried out in the presence of triethylamine, in acetonitrile, at room temperature.

Ultrasound-assisted 1,3-dipolar cycloaddition and cyclopropanation reactions for the synthesis of bis-indolizine and bis-cyclopropane derivatives.

Ultrasound irradiation can promote the 1,3-dipolar cycloaddition reaction of 2-chloropyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile, to afford the indolizine and bis-indolizine derivatives respectively. While the reaction of pyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile under ultrasound irradiation provided, in an unusual manner, cyclopropane and bis-cyclopropane derivatives, respectively. These cycloaddition and cyclopropanation reactions were carried out in the presence of triethylamine, in acetonitrile, at room temperature.

A Novel Strategy for the Synthesis of 3-(N-Heteryl)pyrrole Derivatives

A flexible approach to unknown 1-(1H-pyrrol-3-yl)pyridinium salts with selective control of the substitution patterns, by the reaction of pyridinium ylides with 2H-azirines, is disclosed. 3-(Pyridinium-1-yl)pyrrolides, a new type of stable ylide, were prepared from these salts in high yields by treatment with base. Atmospheric-pressure hydrogenation of the ylides with Adams' catalyst lead to 1-(pyrrol-3-yl)piperidines in good yields.

Synthesis of tetrasubstituted pyridazines via cascade reactions of diazocarbonyl compounds with pyridinium ylides

Reactions of pyridinium ylides with diazocarbonyl compounds involve the formation of functionalized azine intermediates that can undergo intramolecular cyclocondensation into tetrasubstituted pyridazines provided the starting reagents contain carbonyl groups. Reactions of pyridinium ylides with diazo compounds were studied for various substituents in both the substrates.

On the Mechanism of C⇔N Migration of Alkoxycarbonyl Groups in Reactions of Pyridinium Ylides (I) with Isocyanates (II).

On the Mechanism of C⇔N Migration of Alkoxycarbonyl Groups in Reactions of Pyridinium Ylides (I) with Isocyanates (II).

On the mechanism of C ⇄ N migration of alkoxycarbonyl groups in reactions of pyridinium ylides with isocyanates

New examples of reversible C ⇄ N migrations of alkoxycarbonyl groups, which occur in the reactions of pyridinium and 3-(diethylcarbamoyl)pyridinium ylides, viz., derivatives of dimethyl and diethyl malonates, with aryl isocyanates were studied. The mechanism of migration of the methoxycarbonyl group from the carbon atom to the nitrogen atom was considered on the basis of quantum-chemical calculations. The product of the primary attack of the isocyanate group by pyridinium ylide was established to be rearranged with low potential barriers to form carbamate without formation of cyclic intermediate compounds.

Preparation of New Nitrogen-Bridged Heterocycles. 36. Synthesis and Reaction of Dimethyl 4-Thia-1-azatetracyclo[5.4.0.05,11.06,8]undeca-2,9-diene-5,6-dicarboxylate Derivatives

Abstract The title compounds, dimethyl 4-thia-1-azatetracyclo[5.4.0.05,11.06,8]undeca-2,9-diene-5,6-dicarboxylates, were prepared in low to moderate yields by the reactions of various 1-pyridinio[(thiocarbonyl)methylide]s and 3-(1-pyridinio)thiophene-2-thiolates with dimethyl acetylenedicarboxylate in chloroform or benzene at room temperature or at the elevated temperature. Some compounds could also be obtained by heating the corresponding dimethyl 10aH-pyrido[1,2-d][1,4]thiazepine-1,2-dicarboxylates once separated from the reaction of pyridinium ylides with the same reagent. These 4-thia-1-azatetracyclo[5.4.0.05,11.06,8]undeca-2,9-diene derivatives were smoothly thermolyzed in xylene at the reflux temperature to afford dimethyl phthalate and the corresponding thiazole derivatives in good yields. The structures of these 4-thia-1-azatetracyclo[5.4.0.05,11.06,8]undeca-2,9-dienes were mainly identified by their physical and spectral inspections together with mechanistic considerations, and confirmed finally by the X-ray analyses of two compounds.

Electronic regioselectivity in the reactions of pyridinium ylides with tetracyanoethylene

Highly regioselective reactions of pyridinium ylides with tetracyanoethylene occur via an AdN-E mechanism to form Z-isomers of 3-aroyl-3-(1-pyridinio)-1,1,2-tricyano-2-propenides-1, corresponding in structure to 1,4-ylides with maximum charge separation. If the unsaturated nitrite starting material contains a nucleofugal group 1,2-elimination predominates over 1,3-elimination.

Stereochemistry of the reaction of pyridinium ylides with ?,?-unsaturated nitriles

Regioselective and stereoselective methods were developed for the synthesis of 4-aryl-2-oxo-3-(1-pyridinio)-5-cyano-3,4-trans-1,2,3,4-tetrahydropyridin-6-olates from pyridinium ylides and α,Β-unsaturated nitriles. The compounds were also obtained by the condensation of aromatic aldehydes, cyanoacetamide, and pyridinium ylides. It was established that these reactions take place through the corresponding Michael adducts, which undergo heterocyclization in the form of the anti conformers to substituted 3,4-trans-1,2,3,4-tetrahydropyridin-6-olates.

Reactions of pyridinium ylides with aldehydes and with Michael acceptors

1-Methyl and 1-allyl-2,4,6-triphenylpyridinium cations react with aromatic aldehydes at the α-CH2 to give aldol products (7) and (8). The allyl adducts (8) were thermally converted into aldehydes and ketones, whereas thermolysis of (7) took a variety of courses. Zwitterions from 1-methylpyridinium cations were also added Michael-fashion to activated carbon–carbon double bonds.

Heterocyclic ketenethioacetal derivatives. VIII. Synthesis of ketenethioacetals having pyridinium salt (author's transl)

Ketenethioacetal derivatives, 1-[2, 2-bis (methylthio) vinyl] pyridinium iodides, were synthesized by alkylation with methyl iodide of sulfur-containing pyridinium ylides, which were prepared by the reaction of pyridinium ylides with carbon disulfide in the presence of sodium hydroxide.

Heteroaromaticity studies. LIII. Formation of 1,3-oxazine and 2-pyrone derivatives from the reaction of pyridinium ylides with diphenylcyclopropenone

Heteroaromaticity studies. LIII. Formation of 1,3-oxazine and 2-pyrone derivatives from the reaction of pyridinium ylides with diphenylcyclopropenone