256. ω-Halogenomethyl-pyridines, -quinolines, and -isoquinolines. Part I. Preparation

Brown, B. R.; Hammick, D. Ll.; Thewlis, B. H.

doi:10.1039/jr9510001145

Cited by 31 publications

(24 citation statements)

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“…81°C). [35] (X-Heterocyclemethyl) Chloride. General Procedure: These compounds were prepared, as reported in the literature, [36] by precipitating the chlorohydrate salt of the methanol heterocycle from benzene with gaseous HCl.…”

Section: -Quinolinecarbaldehyde and 3-isoquinolinecarbaldehydementioning

confidence: 99%

Synthesis and Characterization of Some Aza[5]helicenes

et al. 2005

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A systematic study on the synthesis and properties of aza- [5]helicenes bearing one or two nitrogen atoms in selected ring positions is reported for the first time. This photochemical approach can be conveniently applied to the preparation of either mono- or diaza[5]helicenes. The aza[5]helicenes were characterized by NMR spectroscopy, X-ray crystallography, emission spectroscopy, and luminescence lifetime. The extremely long triplet lifetime observed (in the range of seconds) makes these molecules promising candidates for practical applications in photo- and optoelectronics

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Section: -Quinolinecarbaldehyde and 3-isoquinolinecarbaldehydementioning

confidence: 99%

Synthesis and Characterization of Some Aza[5]helicenes

et al. 2005

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“…All the evidence produced since Hammick's original work can be accommodated by the ylid mechanism. For example, the reaction has a large carboxylcarbon kinetic isotope effect (3,4), and is faster + co, for the methylbetaine than for the acid itself (5,6).…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of Decarboxylation of some Pyridinecarboxylic Acids in Aqueous Solution

Dunn¹,

Lee²,

Thimm³

1972

Can. J. Chem.

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The first-order rate constants for decarboxylation of picolinic and five substituted picolinic acids in buffered aqueous solution.at 150" and ionic strength 1.0 increase as pH increases above 0, go through a maximum at pH near 1, then level off at about half the maximum. For quinolinic acid at 95" the rate maximum occurs at the isoelectric pH. It is therefore concluded that the anion decarboxylates about half as fast as the isoelectric species. Anion and isoelectric species show similar carboxyl-carbon kinetic isotope and substituent effects, so they probably decarboxylate by similar mechanisms. The methyl betaine of picolinic acid decarboxylates about 200 times faster than the anion. From these facts it is concluded that the isoelectric species which decarboxylates is probably zwitterion rather than neutral acid, and that anion and zwitterion decarboxylate by loss of carbon dioxide to form 2-pyridyl carbanion and ylid, respectively. The slower decarboxylation of isoelectric species compared to betaine suggests that only a small fraction of the isoelectric species is zwitterion. However, qualitative estimates from spectra of the fraction of zwitterion present in the isoelectric species at 150' suggest that this cannot be the whole explanation. The relative reactivities of the 2-and 4-positions are similar for decarboxylation and hydrogen exchange in pyridinium ions, but not in the unprotonated species.Les constantes de vitesse du premier ordre pour la dtcarboxylation de l'acide picolinique et cinq de ses derives substituks, en solution aqueuse tamponnee a 150" et de pouvoir ionique 1.0 augmentent avec un pH au-dessus de 0, passent par un maximum pour un pH proche de 1, et se stabilisent ensuite a environ la moitie de ce maximum. Pour l'acide quinolinique a 95", le maximum de vitesse se produit au pH isoelectrique. On a conclu par consequent que l'anion se decarboxyle a une vitesse qui est de moitie celle de l'espece isoelectrique. L'anion et l'espece isoelectrique montrent des effets similaires de substituants et de cinttique isotopique carboxyle-carbone, aussi les mecanismes de decarboxylation sont probablement voisins. La bttaine methylee de l'acide picolinique a une vitesse de decarboxylation de 200 fois superieure a celle de I'anion. Ces faits ont amenes a conclure que l'espece isoelectrique qui subit la decarboxylation est probablement le zwitterion plut6t que l'acide neutre et que la decarboxylation de I'anion et du zwitterion se fait par perte de gaz carbonique pour donner respectivement le pyridyl-2 carbanion et l'ylure. La dkcarboxylation plus lente de l'espece isoelectrique comparee a la betaine, laisse penser que seule une petite fraction de l'espece isoelectrique est a I'ttat de zwitterion. Toutefois, les estimations qualitatives a partir des spectres de la fraction de zwitterion prisente dans I'espece isoelectrique a 150°, suggere que cette explication ne puisse pas &tre la seule. Les reactivites relatives des positions -2 et -4 sont semblables pour la decarboxylation et l'echange d'hydrogene dans l...

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“…Die Methodik ist daher zur Herstellung grosserer Mengen von isomerenfreieni 2,3,6-Trichlorpyridin (7) aus 1 geeignet. Die 3-Dichlormethylverbindungen 3 und 4 lassen sich, im Gegensatz zu den im Kern halogenfreien Verbindungen [2], ohne Zersetzung aufbewahren. Ahnlich wie sich in einem Gemisch von Salpetersaure/Schwefelsaure 2,6-Dichlorpyridin am C(3) leicht nitrieren lasst [4], kann man auch 2,3,6-Trichlorpyridin (7) an C(5) nitrieren.…”

Section: Die Chlorierung Der 3-chlormethylgruppe In 26-dichlor-und 2unclassified

“…,,28,14 ,. 0,91 ,,53,18 ,,5,207;2,5,. I n cine auf 88-90" erhitzte Schmelze von 92,s g (0,4 mol) 2 werdcn unter LJV-Bestrahlung innerhalb 4-4,5 Std. 150 g (2,11 Gef.…”

Section: H ~L Y C H ( C H 3 ) Z -(Qchtnh-wchj~unclassified

Halogenierte Pyridine II. Reaktionen der 3‐Halogenmethyl‐pyridine

Horn

Mutterer

Weis

1976

Helvetica Chimica Acta

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Halogenated pyridines II. Reactions of 3‐halogenomethyl‐pyridines. The facile syntheis of 3‐halogenomethyl‐pyridines provides an easy access to a variety of new 2, 6‐di‐ and 2, 5, 6‐trihalogented pyridines with various functional groups in the 3‐position of the pyridine ring. Substitution reactions of the 3‐halogenomethyl groups, their Friedel Crafts reactions, and nitrations of the halogenated pyridine ring are reported.

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256. ω-Halogenomethyl-pyridines, -quinolines, and -isoquinolines. Part I. Preparation

Cited by 31 publications

References 0 publications

Synthesis and Characterization of Some Aza[5]helicenes

Synthesis and Characterization of Some Aza[5]helicenes

Kinetics and Mechanism of Decarboxylation of some Pyridinecarboxylic Acids in Aqueous Solution

Halogenierte Pyridine II. Reaktionen der 3‐Halogenmethyl‐pyridine

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