Benzimidazole N-Oxides. V. Reactions of 1,2-Dimethylbenzimidazole 3-Oxide with Acetylenecarboxylates

Takahashi, Shirō; Kanō, Hideo

doi:10.1021/jo01015a041

Cited by 44 publications

(15 citation statements)

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“…Their formation is possible via subsequent C-C bond cleavage, whereas C-N bond fissure can be an alternative pathway of formation of a 2-substituted quinoline. A similar reaction course has been observed for the cycloaddition of DMAD to 1,2-dimethylbenzimidazole 3-oxide [41].…”

Section: Cycloaddition To Carbon-carbon Multiple Bondssupporting

confidence: 71%

“…Cycloaddition of imidazole N-oxides with DMAD gives the expected products of the isoxazoline ring opening [48]. An analogous behavior has been reported for 1-methylbenzimidazole 3-oxide [41,49] and dihydroimidazole N-oxide [50]. More recently, Mlostoń and coworkers reported that N-oxides of imidazoles bearing an electron-withdrawing group at C-4 (ester, acetyl, carboxamide) react with DMAD to give the expected 2-oxobutanedioates, but the products readily undergo addition of water and oxalyl cleavage to (imidazol-2-yl)acetates [51,52].…”

Section: Cycloaddition To Carbon-carbon Multiple Bondssupporting

confidence: 61%

“…Concerning cycloaddition of azoles N-oxides with isocyanates, reactions of 1-methylbenzimidazole 3-oxide with phenyl isocyanate, phenyl isothiocyanate, or even benzonitrile give 2-substituted products of the opening of the initial fivemembered cycloadduct (Scheme 23) [41,49]. The reaction of 1-benzyl-4,5-dimethylimidazole 3-oxide with PhNCO has been reported to give a N-imidazolyl-N,N 0 -diphenylurea derivative, a product of initial cycloaddition, formation of 2-aminoimidazole, and its subsequent reaction with the second molecule of PhNCO [48].…”

Section: Cycloaddition To Carbon-nitrogen Multiple Bondsmentioning

confidence: 99%

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Recent Advances in Cycloaddition Reactions of Heterocyclic N-Oxides

Loska

2017

Topics in Heterocyclic Chemistry

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1,3-Dipolar cycloaddition of N-oxides of azines and azoles has become a reliable and versatile synthetic method of preparation of highly functionalized nitrogen heterocycles. Mechanisms of cycloaddition of N-oxides are outlined, including various reaction pathways available for the initial five-membered cycloadducts. Cycloaddition to multiple carbon-carbon, carbon-nitrogen, and carbon-sulfur bonds is discussed, with particular emphasis on modern methods of selective C-2-functionalization of the heteroaromatic ring.

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Section: Cycloaddition To Carbon-carbon Multiple Bondssupporting

confidence: 71%

Section: Cycloaddition To Carbon-carbon Multiple Bondssupporting

confidence: 61%

Section: Cycloaddition To Carbon-nitrogen Multiple Bondsmentioning

confidence: 99%

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Recent Advances in Cycloaddition Reactions of Heterocyclic N-Oxides

Loska

2017

Topics in Heterocyclic Chemistry

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“…The acylated azomethine ylide 4 becomes isolable when its CN bond is part of an aromatic ring [4] [6] or a 3,4-dihydroisoquinoline system [3]. The ylides 4 are amenable to 1,3-dipolar cycloadditions with suitable dipolarophiles [7].…”

Section: Methodsmentioning

confidence: 99%

A Rearrangement of 3-Pyrazolines as a Missing Link

Finke

Huisgen

Temme

2000

HCA

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Dedicated to Paul von R. Schleyer on the occasion of his 70th birthday The thermal conversion of 4-isoxazolines to 4-oxazolines involves the transposition of two ring members. The ring-contraction and ring-expansion sequence in the reaction 2 3 5 has been previously clarified. The low NÀN bond energy should favor an analogous conversion of 3-pyrazolines 6 to 4-imidazolines 7; the first example of such a transformation is reported here. In the yellow 16, the 3-pyrazoline is part of a pyrazolo-[5,1-a]isoquinoline system. Daylight induces a ring contraction, which affords the 2-isoquinolylaziridine derivative 21. The latter is converted at 658 to the tricyclic 4-imidazoline 26 by a sequence of electrocyclic aziridine ring-opening and 1,5-electrocyclization of a CN-conjugated azomethine ylide 25.

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“…The numerous approaches to obtaining compounds of different classes have been developed, which are based on cycloaddition of various dipolarophiles to nitrones. It should be mentioned that over the past few years, chemistry of isolated nitrones containing no functional substituents at the nitrogen or α-carbon atom as well as cycloaddition reactions of such nitrones have been thoroughly investigated [1][2][3][4][5][6][7][8][9][10][11][12].Unlike this, the nitrone group attached to the heteroatomic substituent at the α-carbon atom is a poorly studied, though interesting, target [13][14][15][16][17][18]. Derivatives of 4,5-dihydro-1H-imidazole 3-oxide, which can be considered as α-aminonitrones, are just such objects.…”

Section: Introductionmentioning

confidence: 99%