1,3-cycloadditions of pyridinium N-arylimides

Huisgen, Rolf; Temme, Robert

doi:10.1002/(sici)1098-1071(1999)10:1<79::aid-hc14>3.0.co;2-m

Cited by 9 publications

(2 citation statements)

References 20 publications

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“…Recently, Huisgen et al − have investigated this reaction. Remarkably, these authors have found that the reaction of 12a with fumaronitrile at room temperature gives risevia the cycloaddition routeto a bridged ring system 13a (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Unexpected Ring Transformation to Pyrrolo[3.2-b]pyridine Derivatives. Fused Azolium Salts. 22

et al. 2003

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2-Arylsulfanyl and 2-benzylsulfanylpyridinium N-arylimides (2) easily prepared from 3-aryltetrazolopyridinium salts (1) with aryl and benzylthiolates, respectively, reacted with various dipolarophiles yielding cycloadducts that underwent transformation to give tetrahydropyrrolo[3,2-b]pyridines (5, 6, and 8) in good yields. A similar rearrangement (formation of 15) was also observed in the case of parent derivatives being unsubstituted in position 2 (12). The abscence of any significant solvent effect, comparison of the sulfur and non-sulfur analogues, as well as the stereoselective nature of the observed ring transformation seem to support a sigmatropic mechanism. Structure elucidation of the products has been carried out by single-crystal X-ray diffraction and 1H NMR experiments.

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Section: Resultsmentioning

confidence: 99%

Unexpected Ring Transformation to Pyrrolo[3.2-b]pyridine Derivatives. Fused Azolium Salts. 22

et al. 2003

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“…Closely related to maleate adduct 11 is 42, which is the major regioisomer in the cycloaddition of 2 to methyl cis-3-cyanoacrylate [4]; it is the 1a-CO 2 Me group of 11 Table 2). We reported recently on the cycloaddition of pyridinium N-phenylimide with dimethyl maleate; adduct 51 smoothly underwent the hydrazo rearrangement to give a tetracyclic aminal [29]. In the framework of structure 49b, removal of the fused benzo ring reduces steric hindrance and allows the [3,3]-sigmatropic shift to proceed.…”

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confidence: 99%

The Astounding Chemistry of a 2-Amino-1,2-dihydroisoquinoline Derivative

Durst

Finke

Huisgen

et al. 2000

HCA

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Dedicated to Professor Albert Eschenmoser on the occasion of his 75th birthday The cycloadducts of isoquinolinium N-phenyl imide 2 with CC bonds are derivatives of 2-amino-1,2-dihydroisoquinoline. Their N b -vinylphenylhydrazine system is amenable to an acid-catalyzed [3,3]-sigmatropic shift; the formation of pentacyclic aminals is exemplified by 6 3 8. The dimethyl maleate adduct 11, C 21 H 20 N 2 O 4 , is exceptional by being converted on treatment with acid to bright-yellow crystals, C 24 H 22 N 2 O 6 (additional C 3 H 2 O 2 ). X-Ray crystal-structure analysis and NMR spectra reveal structure 13, and mechanistic studies indicated an initial b-elimination at the NÀN bond of 11 to yield 18; this step is followed by a retro-Mannichtype cleavage that gives methyl isoquinoline-1-acetate (14) and methyl 2-(phenylimino)acetate (15), according to the sequence C 21 H 20 N 2 O 4 (11) 3 18 3 C 12 H 11 NO 2 (14) C 9 H 9 NO 2 (15). In the second act of the drama, electrophilic attack by 15-H on the ene-hydrazine group of a second molecule of 11 furnishes 13 by a polystep intramolecular redox reaction. All rate constants must be fine-tuned in this reaction cascade to give 13 in yields of up to 78% with an overall stoichiometry: 2 C 21 H 20 N 2 O 4 (11) 3 C 24 H 22 N 2 O 6 (13) C 12 H 11 NO 2 (14) aniline. Interception and model experiments confirmed the above pathway. A by-product, C 33 H 31 N 3 O 6 (62), arises from an acid-catalyzed dimerization of 11 and subsequent elimination of 15.

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[3 + 2] Cycloadditions of Azomethine Imines

Grošelj

Svete

2020

Organic Reactions

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In spite of their late discovery in the middle of 20 th century, the importance of azomethine imines and their [3+2] cycloaddition reactions has grown constantly throughout the decades. Today, [3+2] cycloadditions of azomethine imines have become indispensable in the preparation of pyrazole derivatives with all degrees of saturation. The structural diversity of azomethine imines is wide and comprises acyclic, C , N ‐cyclic, N , N ‐cyclic, and C , N , N ‐cyclic 1,3‐dipoles. Although electron‐deficient dipolarophiles are preferred, electron‐rich dipolarophiles, such as enol ethers and enamines, are also commonly used in these reactions. Compared to cyclocondensation methods and [3+2] cycloadditions with diazoalkanes and nitrile imines, [3+2] cycloadditions with azomethine imines provide access to a greater diversity of pyrazole derivatives with all degrees of saturation. As with other 1,3‐dipolar cycloadditions, a concerted and nearly synchronous mechanism has been proposed for most [3+2] cycloadditions of azomethine imines, although a stepwise mechanism may be viable in some cases. Several examples of asymmetric [3+2] cycloadditions of azomethine imines that afford non‐racemic cycloadducts with high enantioselectivity have been reported. These asymmetric cycloadditions are performed with various types of transition metal catalysts and organocatalysts, and indicate their potential for the asymmetric synthesis of saturated pyrazole derivatives. Finally, many examples of copper‐catalyzed and thermal, strain‐promoted [3+2] cycloadditions of azomethine imines (in particular sydnones) clearly indicate wide applicability of these reactions in bioconjugation, fluorescent labelling, materials functionalization, and other applications outside the realm of pure organic synthesis.

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1,3-cycloadditions of pyridinium N-arylimides

Cited by 9 publications

References 20 publications

Unexpected Ring Transformation to Pyrrolo[3.2-b]pyridine Derivatives. Fused Azolium Salts. 22

Unexpected Ring Transformation to Pyrrolo[3.2-b]pyridine Derivatives. Fused Azolium Salts. 22

The Astounding Chemistry of a 2-Amino-1,2-dihydroisoquinoline Derivative

[3 + 2] Cycloadditions of Azomethine Imines

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