Indications for the occurrence of 2,3-pyridyne as an intermediate

Martens, R. J.; Hertog, H. J. den

doi:10.1016/s0040-4039(00)70924-5

Cited by 28 publications

(19 citation statements)

References 5 publications

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“…151 Reactions of 2,3- and 3,4-didehydropyridines with furan, followed by a lithium amalgam reduction, were found to afford quinoline and isoquinoline, respectively. 194 In contrast, the reactivity of the charged diradicals 37 and 38 has remained largely unexplored until recently.…”

Section: Properties and Reactivitymentioning

confidence: 99%

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

et al. 2013

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Section: Properties and Reactivitymentioning

confidence: 99%

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

et al. 2013

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“…Data for 1 H NMR spectra are reported as follows: chemical shift (δ ppm), multiplicity, coupling constant (Hz) and integration. 13 C NMR spectra were recorded on Bruker spectrometers (125 MHz) and are reported relative to deuterated solvent signals. Data for 13 C NMR spectra are reported in terms of chemical shift and, when necessary, multiplicity, and coupling constant (Hz).…”

Section: Methodsmentioning

confidence: 99%

“…Evaporation under reduced pressure and further purification by preparative thin layer chromatography (2:1 hexanes:EtOAc) afforded 13 as a colorless oil (55% yield, average of two experiments). 13: R f 0.48 (3:1 hexanes:EtOAc); 1 H NMR (500 MHz, CDCl 3 ): δ 8.19 (ddd, J = 4.9, 2.0, 0.8, 1H), 7.49 (ddd, J = 9.0, 7.2, 2.0, 1H), 6.65 (ddd, J = 7.2, 4.9, 0.8, 1H), 6.62 (d, J = 8.7, 1H), 3.82 (t, J = 5.0, 4H), 3.49 (t, J = 5.0, 4H); 13…”

Section: Methodsmentioning

confidence: 99%

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Synthetic studies pertaining to the 2,3-pyridyne and 4,5-pyrimidyne

et al. 2016

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We report synthetic studies pertaining to two heterocyclic aryne intermediates: the 2,3-pyridyne and the 4,5-pyrimidyne. First, a 2,3-pyridyne precursor was readily accessed from 2-pyridone using a known procedure. Subsequently, 2,3-pyridyne generation and trapping were used to access several functionalized pyridines in a regioselective manner. In addition, we report synthetic routes to two isomeric silyltriflates, which were intended to serve as precursors to the 4,5-pyrimidyne. Consecutive 4,5-pyrimidyne generation and trapping experiments were ultimately deemed unfruitful. We expect these findings will promote the use of 2,3-pyridyne and other heterocyclic arynes as building blocks for the synthesis of functionalized heterocycles.

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“…One of the most desirable methods for the generation of the highly labile dehydrobenzerie (benzyne) involves the action of an appropriate dehalogenating agent on air ortho-dihalobenzene (5). This procedure has been corroborated in the heterocyclic series by the successful generation of 3,4-dehydropyridine (3,4-pyridyne) (6) and 2,3-dehydropyridinc (2,3-pyridyne) (7) by the respective treatment of 3-bromo-4-chloropyridine and 3-bromo-2chloropyridine with lithium amalgam at 20" (8). However, the low yield of products resulting from the trapping of these highly reactive dehydropyridines as opposed to the high yield of analogous products formed from dehydrobenzene generated from the action of lithium amalgam on o-bromofluorobenzene is noteworthy.…”

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confidence: 87%

New 2,3‐dihalopyridines. Potential precursors for 2,3‐dehydropyridine

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Borne

Setliff

1967

Journal of Heterocyclic Chem

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One of the most desirable methods for the generation of the highly labile dehydrobenzerie (benzyne) involves the action of an appropriate dehalogenating agent on air ortho-dihalobenzene (5). This procedure has been corroborated in the heterocyclic series by the successful generation of 3,4-dehydropyridine (3,4-pyridyne) (6) and 2,3-dehydropyridinc (2,3-pyridyne) (7) by the respective treatment of 3-bromo-4-chloropyridine and 3-bromo-2chloropyridine with lithium amalgam at 20" (8). However, the low yield of products resulting from the trapping of these highly reactive dehydropyridines as opposed to the high yield of analogous products formed from dehydrobenzene generated from the action of lithium amalgam on o-bromofluorobenzene is noteworthy. These facts suggest that an appropriate bromofluoropyridine or even a fluorochloropyridine might conceivably serve as a more desirable precursor for either a 3,4or a 2,3-dehydropyridine. We wish to report the preparation of some new 2,3-dihalopyridines which could serve in the latter capacity.Bromination of 2-amino-5-methylpyridine (I) in acetic acid at 90" proceeded rapidly to yield a single product, (68%) characterized as 2-amino-3-bromo-5-methylpyridine (11) (9). The absence of n.m.r. absorption assignable to the proton in position 3 (7 = 3.74) in 11 as compared to the appearance of this signal in the spectrum of I confirmed that bromination occurred in the 3-position.Diazotization of I1 directly in 40% fluoboric acid (Method A) by the Schiemann method (10) yielded the hitherto unknown 3-bromo-2-fluoro-5-methylpyridine (111) and 3-bromo-5-methyl-2(1H)pyridone (IV) in 40% and 31% yields respectively. That the formation of IV may be attributed to the hydrolysis of initially formed 111 was established by independent experiment. Treatment of pure 111 with 40% fluoboric acid under the conditions described for Method A resulted in the formation of IV in 38% yield (11). If diazotization of I1 is carried out directly in hexafluorophosphoric acid (12) by a modified Schiemann method (Method B) the fluorobromopyridine I11 is obtained in slightly better (45%) yield together with only trace amounts of the pyridone IV.3-Bromo-2-chloro-5-methylpyridine (V) was conveniently prepared in 46% yield by diazotization of I1 in hydrochloric acid at 0". We observed that careful temperature control is of utmost importance in this reaction since significant amounts of IV are formed also if the diazotization temperature is allowed to rise above 5" (13). However, the steam volatility of V permits its separation from any pyridone contamination.Our route to the previously unreported 2-chloro-3fluoropyridine (VI) involved initial tin and hydrochloric acid reduction of commercially available 2-chloro-3nitropyridinc to 3-amino-2-chloropyridine in 55% yield (14). Subsequent diazotization of the aminopyridine in hydrochloric acid followed by addition of hexafluorophosphoric acid, (12) yielded the stable solid diazonium hexafluorophosphate (VII) in 86% yield. Decomposition of VII in preheated mineral oil pr...

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Indications for the occurrence of 2,3-pyridyne as an intermediate

Cited by 28 publications

References 5 publications

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

Synthetic studies pertaining to the 2,3-pyridyne and 4,5-pyrimidyne

New 2,3‐dihalopyridines. Potential precursors for 2,3‐dehydropyridine

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