Synthesis of 1,3-diazepines and ring contraction to cyanopyrroles

Several tetrazolo[1,5-a]pyridines/2-azidopyridines undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes, as well as ring cleavage to cyanovinylketenimines, in low temperature Ar matrices. 6,8-Dichlorotetrazolo[1,5-a]pyridine/2-azido-3,5-dichloropridine undergoes ready exchange of the chlorine in position 8 (3) with ROH/RONa. 8-Chloro-6-trifluoromethyltetrazolo[1,5-a]pyridine undergoes solvolysis of the CF(3) group to afford 8-chloro-6-methoxycarbonyltetrazolo[1,5-a]pyridine. Several tetrazolopyridines/2-azidopyridines afford 1H- or 5H-1,3-diazepines in good yields on photolysis in the presence of alcohols or amines. 5-Chlorotetrazolo[1,5-a]pyridines/2-azido-6-chloropyridines and undergo a rearrangement to 1H- and 3H-3-cyanopyrroles and, respectively. The mechanism of this rearrangement was investigated by (15)N-labelling and takes place via transient 1,3-diazepines. The structures of 6,8-dichloro-tetrazolo[1,5-a]pyridine, 6-chloro-8-ethoxytetrazolo[1,5-a]pyridine, dipyrrolylmethane, and 2-isopropoxy-4-dimethylamino-5H-1,3-diazepine were determined by X-ray crystallography. In the latter case, this represents the first reported X-ray crystal structure of a 5H-1,3-diazepine.     

5-取代氧化呋咱并[3,4-b]吡啶衍生物的合成与表征

以廉价易得的2,6-二氯吡啶为原料,经过硝化、叠氮化、热解环化步骤得到中间体[1,2,5]噁二唑并[3,4-e]四唑并[1,5-a]吡啶-3-氧化物(4b),再与浓硫酸/硝酸钾、甲醇钠和甲胺水溶液反应分别得到5-取代的氧化呋咱并[3,4-b]吡啶衍生物5~7。 研究了化合物4b结构的稳定性,发现其中的氧化呋咱环在强酸性、强碱性和弱碱性条件下较稳定,而吡啶环与叠氮基形成的四唑环结构则不太稳定。     

2-Quinolyl- and 1-isoquinolylnitrenes: ring expansion and ring opening in heteroarylnitrenes

Argon matrix photolysis of tetrazolo[1,5-a]quinoline 8 and tetrazolo[5,1-a]isoquinoline 7 causes nitrogen elimination and ring expansion to 1,3-diazabenzo[d]cyclohepta-1,2,4,6-tetraene 13. The photolysis of tetrazolo[5,1-a]isoquinoline 7 also causes ring opening to o-cyanophenylketenimine 22. Mechanisms of ring opening of heteroarylnitrenes are discussed.     

Molecular iodine catalyzed synthesis of tetrazolo[1,5-a]-quinoline based imidazoles as a new class of antimicrobial and antituberculosis agents

A series of some new tetrazolo[1,5-a]quinoline based tetrasubstituted imidazole derivatives 6a-1 have been synthesized by a reaction of tetrazolo[1,5-a]quinoline-4-carbaldehyde 3a-d,benzil 4,aromatic amine 5a-c and ammonium acetate in the presence of iodine through one-pot multi-component reaction(MCR) approach.All the derivatives were screened for antimicrobial and antituberculosis activities and results worth further investigations.     

Silicon-mediated highly efficient synthesis of 1, 8-dioxo-octahydroxanthenes and their transformation to novel functionalized pyrano-tetrazolo [1, 5-a] azepine derivatives

A facile and highly efficient protocol for the synthesis of 1,8-dioxo-octahydroxanthene derivatives was achieved through cascade Knoevenagel-Michael condensations and cyclo-dehydration reaction utilizing tetrachlorosilane（TCS） as catalyst under mild conditions.Reaction of the titled compounds with TCSNaN₃ to give novel functionalized pyrano[3,2-c]tetrazolo[1,5-a]azepine derivatives is also described.     

One-Step conversion of pyridine N-oxides to tetrazolo[1,5-a]pyridines

Pyridine N-oxides were converted to tetrazolo[1,5-a]pyridines in good to excellent yield by heating in the presence sulfonyl or phosphoryl azides and pyridine in the absence of solvent. Various sulfonyl and phosphoryl azides were screened for reactivity under a standard set of conditions. Diphenyl phosphorazidate was the most convenient reagent and gave high yields. Reaction optimization, scope, and scalability are discussed.     

Anomeric Stereoauxiliary Cleavage of the C−N Bond of d-Glucosamine for the Preparation of Imidazo[1,5-a]pyridines

The targeted cleavage of the C−N bonds of alkyl primary amines in sustainable compounds of biomass according to a metal-free pathway and the conjunction of nitrogen in the synthesis of imidazo[1,5-a]pyridines are still highly challenging. Despite tremendous progress in the synthesis of imidazo[1,5-a]pyridines over the past decade, many of them can still not be efficiently prepared. Herein, we report an anomeric stereoauxiliary approach for the synthesis of a wide range of imidazo[1,5-a]pyridines after cleaving the C−N bond of d -glucosamine (α-2° amine) from biobased resources. This new approach expands the scope of readily accessible imidazo[1,5-a]pyridines relative to existing state-of-the-art methods. A key strategic advantage of this approach is that the α-anomer of d -glucosamine enables C−N bond cleavage via a seven-membered ring transition state. By using this novel method, a series of imidazo[1,5-a]pyridine derivatives (>80 examples) was synthesized from pyridine ketones (including para-dipyridine ketone) and aldehydes (including para-dialdehyde). Imidazo[1,5-a]pyridine derivatives containing diverse important deuterated C(sp²)−H and C(sp³)−H bonds were also efficiently achieved.     

Photochemical ring expansion of 4-azidouracil: a route to 5H-1,3,5-triazepin-2,4-dione in the nucleoside series

Under aqueous conditions, 4-azidouracil/tetrazolo[1,5-c]pyrimidin-5(6H)-one nucleosides undergo a very efficient photochemical nitrogen elimination and ring expansion to 1,3,5-triazepin-2,4-dione nucleosides whose structure has been confirmed by X-ray crystallography. In contrast, when the photolysis was attempted under anhydrous conditions in the presence of a nucleophile, a ring contraction reaction occurred, affording 2-oxoimidazolone nucleosides. A mechanism to account for the formation of ring expansion and contraction reactions and involving a carbodiimide intermediate is proposed which is reminiscent of the known photochemical behavior of 2-azidopyridines/tetrazolo[1,5-a]pyridines.     

Au(i)-catalyzed and iodine-mediated cyclization of enynylpyrazoles to provide pyrazolo[1,5-a]pyridines

Pyrazolo[1,5-a]pyridines and 6-iodopyrazolo[1,5-a]pyridines were synthesized by gold-catalyzed and iodine-mediated cyclization of enynylpyrazoles in good to excellent yields, respectively. The iodinated adducts were further converted to 6-arylpyrazolo[1,5-a]pyridines via Suzuki-Miyaura coupling reaction and 6-cyanopyrazolo[1,5-a]pyridine by Ullmann condensation reaction. One of the cyclization adducts, 2-(4-fluorophenyl)pyrazolo[1,5-a]pyridine, was converted to a p38 kinase inhibitor, 2-(4-fluorophenyl)-3-(4-pyridinyl)pyrazolo[1,5-a]pyridine, in two steps.     

Cascade intermolecular Michael addition-intramolecular azide/internal alkyne 1,3-dipolar cycloaddition reaction in one pot

A rapid one-pot protocol for the synthesis of indole-based polyheterocycles via a sequential Lewis acid catalyzed intermolecular Michael addition and an intramolecular azide/internal alkyne 1,3-dipolar cycloaddition reaction has been described. The generality of the method has been demonstrated by treating a series of aromatic/aliphatic 2-alkynyl indoles with substituted (E)-1-azido-2-(2-nitrovinyl)benzenes to furnish annulated tetracyclic indolo[2,3-c][1,2,3]triazolo[1,5-a][1]benzazepines in good yields.     

Synthesis and characterization of new O,O‐diethyl phosphorothioates derived from substituted tetrazolo[1,5‐a]quinolin‐ 4‐ylmethanol derivatives

A simple and convenient method is developed for the synthesis of new O,O‐diethyl O‐(substituted tetrazolo[1,5‐a]quinolin‐4‐yl)methyl phosphorothioates, which has been synthesized for the first time from tetrazolo[1,5‐a] quinolines via tetrazolo[1,5‐a]quinolin‐4‐ylmethanol derivatives. The structures of the all newly synthesized compounds were elucidated by analytical and spectral methods. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:436–441, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20570     

咪唑并吡啶化合物的合成研究进展

咪唑并吡啶类化合物是一类非常重要的含氮稠杂环化合物, 在医药、农药和染料工业有着广泛的应用. 该类化合物由于其特定的生理活性以及和吲哚、氮杂吲哚等在结构上的类似性, 引起了人们广泛的兴趣. 常见的咪唑并吡啶类化合物有咪唑并[1,2-a]吡啶、咪唑并[1,5-a]吡啶、咪唑并[4,5-b]吡啶和咪唑并[4,5-c]吡啶等类型. 以咪唑并[1,2-a]吡啶和咪唑并[1,5-a]吡啶化合物为例, 阐述该类化合物近十年来的合成研究进展.     

咪唑并吡啶类化合物的合成及其应用*

咪唑并吡啶类化合物具有与吲哚、氮杂吲哚等类似的特殊结构和良好的生物活性,在医药和农药工业有着广泛的应用,成为有机化学家和药物化学家的研究热点。咪唑并吡啶类化合物主要有咪唑并[4,5-b]吡啶、咪唑并[4,5-c]吡啶、咪唑并[1,2-a]吡啶和咪唑并[1,5-a]吡啶等4个类型。本文阐述了近年来咪唑并吡啶类化合物的合成研究进展和应用情况,主要介绍了咪唑并[4,5-b]吡啶和咪唑并[4,5-c]吡啶这两类化合物的合成方法和在医药及农药领域的应用。     

1-Phenyl-2,3-diazacycl[3,2,2]azine,a new 10-π electron system. Involvement of 3,5-didehydroimidazo[1,5-a]pyridine?

3-Ethylthioimidazo[1,5-a]pyridine reacts with butyl lithium followed by benzonitrile to give the new 10-π electron system, 1-phenyl-2,3-diazacycl[3,2,2]azine, possibly via 3,5-didehydroimidazo[1,5-a] pyridine.     

A simple and efficient synthesis of new fluorophore 4-hydroxy pyrazolo[1,5-a]pyridines through a tandem reaction

The cascade reaction of ethyl pyrazole-5-carboxylate with α, β-unsaturated ester leading to 4-hydroxy pyrazolo[1,5-a]pyridine derivatives has been developed. A possible mechanism is proposed. The resulting pyrazolo[1,5-a]pyridines present strong fluorescence in solutions.     

Studies on benzodiazines

The oxidation of tetrazolo[1,5-a]quinoxaline and its 7,8-dimethyl derivative and of s-triazolo[4,3-a]quinoxaline has given the corresponding quinoxalin-4-ones. A calculation of the localization energies has shown the radical nature of the attack in position 4, and this has been confirmed by the results of the oxidation of 4-methyl- and 4-phenyl-quinoxalines.For Communication XIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 6, pp. 851–854, June, 1970.     

A direct method for the substitution of imidazo[1,5-a]pyridines at position 5

3-Ethylthioimidazo[1,5-a]pyridine lithiates at carbon 5. Quenching of the anion with an electrophile followed by desulphurisation gives 5-substituted imidazo[1,5-a]pyridines.     

Synthesis of some fused quinoline derivatives

Summary Preparations of the novel fused dimethoxyquinoline derivatives of furo[2,3-b]quinoline (5),s-triazolo[4,3-a]quinoline (8) and tetrazolo[1,5-a]quinoline (10) from 6,7-dimethoxy-3-car-boxyquinoline-1-oxide (1) are reported.

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Synthese kondensierter Chinolinderivate

Zusammenfassung Die Synthese der neuen kondensierten Dimethoxy-Chinolinderivate Furo[2,3-b]chinolin (5),s-Triazolo[4,3-a]chinolin (8) und Tetrazolo[1,5-a]chinolin (10) aus 6,7-Dimethoxy-3-carboxychinolin-1-oxid (1) wird beschrieben.

     

Studies toward the total synthesis of nagelamide K

A stereocontrolled strategy toward the synthesis of nagelamide K has been developed. The dimeric imidazole acrylate, diimidazolidenesuccinate, was constructed as a synthetic precursor by a Ni-catalyzed coupling reaction; the microwave-promoted intramolecular aza-Michael addition afforded the imidazo[1,5-a]pyridine core structure of nagelamide K in high stereoselectivity. A detaurine-dediamino analogue of nagelamide K has been prepared.     

吡唑并[1,5-α]吡啶类化合物的合成及其体外受体结合分析

以吡唑并[1,5-α]吡啶-3-甲醛和N-甲酰基哌嗪为原料,经过还原胺化、水解和N-烷基化反应,合成了3-(4-苄基哌嗪-1-基甲基)吡唑并[1,5-α]吡啶、3-[4-(4-氯苄基)哌嗪-1-基甲基]吡唑并[1,5-α]吡啶和3-[4-(4-甲氧基苄基)哌嗪-1-基甲基]吡唑并[1,5-α]吡啶,通过1H NMR、ESI MS等技术手段对中间体及3个目标化合物进行了表征,并通过体外受体结合实验,测定3个目标化合物对多巴胺D4.2受体的亲和常数(Ki)分别为1.6、7.2、65 nmol/L;对D2受体的亲和常数分别为1920、5320和9800 nmol/L;对D3受体的亲和常数分别为1710、4270和5600 nmol/L。结果表明,3-(4-苄基哌嗪-1-基甲基)吡唑并[1,5-α]吡啶对多巴胺D4受体具有较高的亲和性与选择性,是多巴胺D4受体潜在的配基。