Rhodium-Catalyzed Transannulation of 1,2,3-Triazoles with Nitriles

Horneff, Tony; Chuprakov, Stepan; Chernyak, Natalia; Gevorgyan, Vladimir; Fokin, Valery V.

doi:10.1021/ja805079v

Cited by 500 publications

(242 citation statements)

References 29 publications

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“…5,[17][18][19][20][21] However, in our case, the conversion of the copper-triazolyl intermediate A into the corresponding triazol does not take place. Presumably, intermediate A could be transformed into the ketenimide-copper species D through species B or C. 5,19,21 Protonation of the ketenimide would trigger a rearrangement and cyclization of the organic fragment to give F (two resonance forms shown in Scheme 1) in a similar, but not identical, manner to that previously proposed by Gevorgyan and co-workers for the formation of pyrroles. 22 A 1,2-hydrogen shift 23 would afford G from which 3a would be formed with the concomitant release of the catalyst.…”

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confidence: 57%

Regioselective Formation of 2,5-Disubstituted Oxazoles Via Copper(I)-Catalyzed Cycloaddition of Acyl Azides and 1-Alkynes

et al. 2010

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Abstract:The reaction of 1-alkynes with acylazides in the presence of [Tpm *,Br Cu(NCMe)]BF4 (Tpm *,Br = tris(3,5-dimethyl-4-bromopyrazolyl)methane) as the catalyst provides 2,5-oxazoles in moderate to high yields. This is a novel transformation of CuAAC type, that constitutes a significant variation of the commonly observed [3+2] cycloaddition reaction to yield 1,2,3-triazoles.The copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction constitutes one of the most interesting examples of click chemistry.1 Since its discovery, 2 the CuAAC methodology has become a powerful tool with growing applications in different areas such as polymer and material sciences, bioconjugation and medicinal chemistry. 3 We have recently developed a catalytic system for this transformation based on a well-defined and stable Cu(I) complex: [Tpm *,Br Cu(NCMe)]BF 4 (Tpm *,Br = tris(3,5-dimethyl-4-bromopyrazolyl)methane ligand) that efficiently promoted the formation of N-sulfonyl-1,2,3-triazoles from sulfonyl azides and 1-alkynes under mild conditions (eq 1). 4 Encouraged by these results, we decided to expand the scope of this reaction using acyl azides since the formation of the corresponding N-benzoyl-1,2,3-triazoles by the [3+2] azidealkyne cycloaddition has resulted elusive to date. 5 Under the protocol used for the synthesis of N-sulfonyltriazoles, 4 phenylacetylene (1.2 mmol, 1) and benzoyl azide (1.0 mmol, 2) were reacted in chloroform at 40 ºC in the presence of catalytic amounts (5 mol%) of [Tpm *,Br Cu(NCMe)]BF 4 . 6 After 24 h, azide was consumed as inferred from FTIR spectroscopy of the reaction mixture, from which three compounds were identified. One of them was benzamide, PhCONH 2 (29% yield by NMR) 7 resulting from the decomposition of the initial azide. The other two compounds 3a and 4a, were obtained in a 10:1 ratio and showed all resonances in the 8.2-7.2 ppm region in the 1 H NMR spectrum. However, neither the carbonyl resonance nor the (CO) band were observed in the 13 C NMR and the FTIR spectra, respectively. Therefore the expected formation of the N-benzoyl-1,2,3-triazol seemed to have failed following this route. A second experiment carried out using p-Me(C 6 H 4 )CON 3 as the azide led to the same observations: two compounds 3b and 4b (along with the corresponding amide derived from that azide) that lacked from the characteristic spectroscopic data typical of the expected triazoles were isolated. In order to ascertain the nature of the new compounds obtained, single crystals of 3b and 4a were grown and their structures unambiguously confirmed by X-ray diffraction analysis.7 To our surprise, they were identified as the oxazoles shown in Scheme 1, the NMR data being in complete agreement with those formulations. 1a R = Ph, 3a R = p-Tol, 3b R = Ph, 4a R = p-Tol, 4b R = Ph, 5a R = p-Tol, 5b R = Ph, 2a R = p-Tol, 2b Scheme 1. Top: catalytic formation of oxazoles from direct reaction of phenylacetylene and benzoyl azide. Bottom: X-ray structures of oxazoles 3b (left) and 4a (right).

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confidence: 57%

Regioselective Formation of 2,5-Disubstituted Oxazoles Via Copper(I)-Catalyzed Cycloaddition of Acyl Azides and 1-Alkynes

et al. 2010

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“…[5,6] As one of attractive synthetic methods for a diversity of target molecules, the metal-catalyzed [2+2+1] annulation of alkynes, nitriles and nitrogen atoms from azides was known (Scheme 1a). [7] The method, however, can stand further improvement due to the requirements of high reaction temperature and tedious procedures, and the limitation of the substrate generality (terminal alkynes only). Although a metal-free multicomponent approach to highly substituted imidazoles from internal alkynes, aldehydes, and ammonium acetate with or without anilines has been reported very recently, this procedure was demonstrated only for the synthesis of 4,5-diarylimidazoles.…”

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confidence: 99%

Metal‐Free [2+2+1] Annulation of Alkynes, Nitriles and Nitrogen Atoms from Iminoiodanes for Synthesis of Highly Substituted Imidazoles

et al. 2015

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“…46 Consequently, as one of alternative methods, a metal-catalyzed [2+2+1] annulation of alkynes, nitriles and N-atoms from azides has been developed. 47,48 This method, however, can stand further improvement due to high reaction temperature, tedious procedures, and the limitation of the substrate generality (terminal alkynes only). Therefore, we have extended the abovementioned [2+2+1] cycloaddition-type method (Section 3.1) 11 to the synthesis of imidazole from alkynes, nitriles and N-atoms from N-tosyliminophenyliodane (PhINTs) (Scheme 15).…”

Section: [2+2+1] Synthesis Of Imidazolesmentioning

confidence: 99%

Metal-free syntheses of oxazoles and their analogues based on λ3-iodane-mediated cycloisomerization/functionalization reactions or [2+2+1] cycloaddition type reactions

Saitô¹

2017

Arkivoc

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As a metal-free construction of oxazoles and furans concomitant with the introduction of oxygen functional groups or fluorine atoms into the side chains, we have developed λ 3 -iodane-mediated cycloisomerization/functionalization reactions of propargyl compounds. In these reactions, aryl-λ 3 -iodane ArI(X)Y works not only as a donor of heteroatomic functional groups but also as an activator of carbon-carbon triple bonds. Therefore, this methodology is not required any transition metal catalysts, which are frequently used in previous methods. Furthermore, this methodology can be extended to λ 3 -iodane-mediated [2+2+1] cycloaddition type reactions of alkynes, nitriles and heteroatoms for metal-free formation of oxazoles and imidazoles.

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Rhodium-Catalyzed Transannulation of 1,2,3-Triazoles with Nitriles

Abstract: Stable and readily available 1-sulfonyl triazoles are converted to the corresponding imidazoles in good to excellent yields via a rhodium(II)-catalyzed reaction with nitriles. Rhodium iminocarbenoids are proposed intermediates.

Cited by 500 publications

References 29 publications

Regioselective Formation of 2,5-Disubstituted Oxazoles Via Copper(I)-Catalyzed Cycloaddition of Acyl Azides and 1-Alkynes

Regioselective Formation of 2,5-Disubstituted Oxazoles Via Copper(I)-Catalyzed Cycloaddition of Acyl Azides and 1-Alkynes

Metal‐Free [2+2+1] Annulation of Alkynes, Nitriles and Nitrogen Atoms from Iminoiodanes for Synthesis of Highly Substituted Imidazoles

Metal-free syntheses of oxazoles and their analogues based on λ3-iodane-mediated cycloisomerization/functionalization reactions or [2+2+1] cycloaddition type reactions

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