Facile Synthesis of Polysubstituted Oxazoles via A Copper-Catalyzed Tandem Oxidative Cyclization

Wan, Changfeng; Zhang, Jintang; Wang, Sujing; Fan, Jinmin; Wang, Zhiyong

doi:10.1021/ol100688c

Cited by 155 publications

(60 citation statements)

References 52 publications

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“…(3aR',4R',6S',6aS')-4-Acetyl-2,6-diphenyl-5-phthalimidotetrahydropyrrolo[3,4-c]pyrrole-1,3(2H,3aH) 2H, m, H-o). The spectrum reported by Herrera et al [23] is in good accord with these results.…”

Section: Thermal Transformations Of Aziridines 1b-f In the Absence Ofsupporting

confidence: 84%

Intra- and intermolecular thermal transformations of 2-acyl- and 2-alkoxycarbonyl-N-phthalimidoaziridines

Кузнецов

Voronin

2011

Chem Heterocycl Comp

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Heating 2-acyl-and 2-alkoxycarbonyl-N-phthalimidoaziridines leads to substituted oxazoles in 45-65% yield. Only esters of oxazolecarboxylic acids are formed when the aziridine contains acyl and alkoxy groups. The thermolysis of the same aziridines in the presence of N-phenylmaleimide and the dimethyl ester of acetylenedicarboxylic acid gives both oxazoles and the products of 1,3-dipolar cycloaddition from aziridines with two substituents at the carbon atoms but only oxazoles from trisubstituted aziridines.The thermally or photochemically induced dissociation of the C−C bond in the strained aziridine ring leads to 1,3-dipoles, which have been termed azomethinylids [1]. The addition of these species at multiple bonds of dipolarophiles yields various five-membered nitrogen heterocycles [2]. The generation of azomethinylids upon heating derivatives of N-phthalimidoaziridine and subsequent 1,3-dipolar cycloaddition have been demonstrated experimentally [3][4][5]. On the other hand, heating N-phthalimidoaziridines having acyl [6] or alkoxycarbonyl substituents [7] at the carbon atoms of the aziridine ring in the absence of dipolarophiles leads to oxazoles, which may be attributed to a 1,5-electrocyclization of the intermediate acylazomethinylids accompanied by loss of the phthalimide group.Thus, two types of thermal transformations are possible for acyl and alkoxycarbonyl derivatives of N-phthalimidoaziridine: 1) 1,3-dipolar cycloaddition and 2) rearrangement to give oxazoles. These reactions may compete and their preparative value will depend on which pathway predominates. In the present work, we studied both the intra-and intermolecular thermal transformations of 2-acyl-and 2-alkoxy-N-phthalimidoaziridines.We selected aziridines 1a-f for this study. The corresponding oxazole has already been obtained in 60% yield upon heating aziridine 1a [6]. However, the reaction of this aziridine with dipolarophiles has not been investigated. Aziridines 1b,c were selected in light of the possibility of obtaining not readily available spirofused heterocyclic structures as the result of 1,3-dipolar cycloaddition. We considered the possibility of _______ * Dedicated to Leonid Isaakovich Belen'kii on the occasion of his eightieth birthday.

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Section: Thermal Transformations Of Aziridines 1b-f In the Absence Ofsupporting

confidence: 84%

Intra- and intermolecular thermal transformations of 2-acyl- and 2-alkoxycarbonyl-N-phthalimidoaziridines

Кузнецов

Voronin

2011

Chem Heterocycl Comp

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“…[12] Recently, interesting reactions of benzylamines and o-carbonylanilines were successfully exploited to synthesize 2-arylquinazolines through the amination of C(sp 3 )ÀHb onds under oxidative conditions (Scheme 1a). [13] As an ongoing effort to synthesizeC ÀN bondsa nd heterocycles, [6,14] we herein report novel ande fficient access to 2,4-disubstituted quinazolines startingf rom onitroacetophenones and benzylamineso ra minoa cids under catalysis of commercially availableP d/C( palladium nanoparticles supported on activated carbon)( Scheme 1b).The initial experiment was performed with am odel reaction betweenbenzylamine( 1a)a nd o-nitroacetophenone(2a)c atalyzed by Pd/C in toluene ( Table 1). Given that hydrogen-transfer reactions are usually performed under alkaline conditions, we employed different bases as additives.…”

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confidence: 99%

Heterogeneous Palladium‐Catalyzed Hydrogen‐Transfer Cyclization of Nitroacetophenones with Benzylamines: Access to C−N Bonds

et al. 2016

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The first Pd/C‐catalyzed oxidative C(sp3)−H bond amination of o‐nitroacetophenones with benzylamines or amino acids proceeding through C−N bond cleavage followed by C−N bond formation by a hydrogen‐transfer strategy was developed. These transformations proceeded smoothly in water to afford the desired quinazolines in moderate to good yields. This protocol has a broad substrate scope and good tolerance of air, offers excellent recyclability of the catalyst, and does not need any additional oxidant, ligand, or base; the combination of all of these factors give a new and practical avenue for multiple C−N bond formation. Moreover, a hot filtration experiment indicated that heterogeneous palladium nanoparticles during the reaction are the active species.

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“…This indicated that the reaction should undergo a radical pathway. Based on the results described above and previous reports [27,28,45,46], a plausible mechanism for this decarboxylative cyclization was proposed as follows (Scheme 2). Initially, compound A, formed by the substitution reaction of 1a with 2a, which can be transformed following two pathways: (a) I + , generated by the oxidation of iodine, could oxidize A to radical intermediate B, which eliminates one molecular of CO 2 to generate radical C, which is further oxidized to imine D or its isomer E. Subsequently, F is obtained by intramolecular nucleophilic addition of E. Finally, the desired product (3a) is given by deprotonation and oxidation of F; (b) G is formed from the oxidation of A.…”

Section: Research Of the Reaction Mechanismmentioning

confidence: 88%

Metal-free synthesis of polysubstituted oxazoles via a decarboxylative cyclization from primary α-amino acids

Guo

Zha

et al. 2013

sustain chem process

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Background: The ubiquitous oxazoles have attracted more and more attention in both industrial and academic fields for decades. This interest arises from the fact that a variety of natural and synthetic compounds which contain the oxazole substructure exhibit significant biological activities and antiviral properties. Although various synthetic methodologies for synthesis of oxazols have been reported, the development of milder and more general procedure to access oxazoles is still desirable. Results: In this manuscript, a novel method for synthesis of polysubstituted oxazoles was developed from metalfree decarboxylative cyclization of easily available primary α-amino acids with 2-bromoacetophenones. Conclusions:The method was simple, and this reaction could be carried out smoothly under mild and metal-free conditions. By virtue of this method, various polysubstituted oxazoles were obtained from the primary α-amino acids with moderate yields.

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Facile Synthesis of Polysubstituted Oxazoles via A Copper-Catalyzed Tandem Oxidative Cyclization

Cited by 155 publications

References 52 publications

Intra- and intermolecular thermal transformations of 2-acyl- and 2-alkoxycarbonyl-N-phthalimidoaziridines

Intra- and intermolecular thermal transformations of 2-acyl- and 2-alkoxycarbonyl-N-phthalimidoaziridines

Heterogeneous Palladium‐Catalyzed Hydrogen‐Transfer Cyclization of Nitroacetophenones with Benzylamines: Access to C−N Bonds

Metal-free synthesis of polysubstituted oxazoles via a decarboxylative cyclization from primary α-amino acids

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