Silver‐Catalyzed Nitrogenation of Alkynes: A Direct Approach to Nitriles through CC Bond Cleavage

Shen, Tao; Wang, Teng; Qin, Chong; Jiao, Ning

doi:10.1002/ange.201300193

Angewandte Chemie

2013

DOI: 10.1002/ange.201300193

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Silver‐Catalyzed Nitrogenation of Alkynes: A Direct Approach to Nitriles through CC Bond Cleavage

Tao Shen

Teng Wang

Chong Qin

et al.

Abstract: Dreifach gebunden und doch gelöst! Eine silberkatalysierte Nitrogenierung überführt Alkine unter CC‐Bindungsspaltung direkt in Nitrile. Dieser neuartige Ansatz erweitert das Anwendungsspektrum von Alkinen in der organischen Synthese und liefert wichtige Einblicke in die Mechanismen von Nitrogenierungen.

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Cited by 54 publications

(23 citation statements)

References 105 publications

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“…[8] Thus, the group of Jiao recently made the remarkable observation that alkynes (1; R = alkyl, aryl, alkenyl) react with TMSN 3 in the presence of Ag 2 CO 3 as catalyst to form nitriles (2; Scheme 1). [9] The same group has reported the cleavage of the aryl-alkyne C(sp 2 )À C(sp) bond of alkynes (1) using [Au(PPh 3 )Cl] and AgCO 3 in the presence of H 2 O and trifluoroacetic acid (TFA) to form carboxamides. [10] The formation of nitriles (2) [9] and carboxamides (3) [10] was proposed to proceed by nucleophilic addition of azide to (h 2 -alkyne)metal complexes to form the intermediates 4 a,b, with subsequent protonolysis to give the alkenyl azides 5 (Scheme 2).…”

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confidence: 99%

“…Scheme 1. Synthesis of nitriles (2) [9] and carboxamines (3) [10] from alkynes (1) by aryl-alkyne C(sp 2 )ÀC(sp) bond cleavage. DMSO = dimethylsulfoxide, TFA = trifluoroacetic acid, TMS = trimethylsilyl.…”

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confidence: 99%

“…[9] The same group has reported the cleavage of the aryl-alkyne C(sp 2 )À C(sp) bond of alkynes (1) using [Au(PPh 3 )Cl] and AgCO 3 in the presence of H 2 O and trifluoroacetic acid (TFA) to form carboxamides. [10] The formation of nitriles (2) [9] and carboxamides (3) [10] was proposed to proceed by nucleophilic addition of azide to (h 2 -alkyne)metal complexes to form the intermediates 4 a,b, with subsequent protonolysis to give the alkenyl azides 5 (Scheme 2). The nitriles 2 could then be produced by a 1,3-dipolar cycloaddition and subsequent fragmentation of 6.…”

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confidence: 99%

“…Mechanistic proposal for the formation of 2 and 3. [9,10] Scheme 3. Synthesis of N-aryltetrazoles (8) from alkynes (1).…”

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confidence: 99%

“…[10] The formation of nitriles (2) [9] and carboxamides (3) [10] was proposed to proceed by nucleophilic addition of azide to (h 2 -alkyne)metal complexes to form the intermediates 4 a,b, with subsequent protonolysis to give the alkenyl azides 5 (Scheme 2). The nitriles 2 could then be produced by a 1,3-dipolar cycloaddition and subsequent fragmentation of 6.…”

mentioning

confidence: 99%

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Gold‐Catalyzed Synthesis of Tetrazoles from Alkynes by CC Bond Cleavage

Gaydou

Echavarren

2013

Angewandte Chemie

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Cycloadditions of azides with alkynes to form triazoles under thermal conditions (Huisgen cycloaddition) [1] or in the presence of copper [click reaction, copper-catalyzed azidealkyne cycloaddition (CuAAC)] [2,3] are reactions of fundamental importance in organic chemistry. Triazoles can also be obtained by means of ruthenium, [4] silver, [5] and iridium [6] catalysis, as well as by a zinc-mediated process. [7] In sharp contrast, very different reactivity has been observed in the reaction of terminal alkynes with TMSN 3 in the presence of group 11 metal salts and complexes. [8] Thus, the group of Jiao recently made the remarkable observation that alkynes (1; R = alkyl, aryl, alkenyl) react with TMSN 3 in the presence of Ag 2 CO 3 as catalyst to form nitriles (2; Scheme 1). [9] The same group has reported the cleavage of the aryl-alkyne C(sp 2 )À C(sp) bond of alkynes (1) using [Au(PPh 3 )Cl] and AgCO 3 in the presence of H 2 O and trifluoroacetic acid (TFA) to form carboxamides. [10] The formation of nitriles (2) [9] and carboxamides (3) [10] was proposed to proceed by nucleophilic addition of azide to (h 2 -alkyne)metal complexes to form the intermediates 4 a,b, with subsequent protonolysis to give the alkenyl azides 5 (Scheme 2). The nitriles 2 could then be produced by a 1,3-dipolar cycloaddition and subsequent fragmentation of 6. In the presence of TFA, protonation of 5 would form 7, which could evolve by a Schmidt rearrangement [11][12][13] to give the amides 3. A somewhat related cleavage of triple bonds to form nitriles has been reported using TMSN 3 and Niodosuccinimide, and was proposed to proceed via 2-iodo-2H-azirines. [14] We now report that by using the JohnPhos/gold(I) catalyst A, [15] which allows performing reactions in the absence of Ag I , the N-aryltetrazoles 8 are obtained from 1 by C À C bond cleavage with the concomitant insertion of four nitrogen atoms (Scheme 3). In this transformation gold plays a dual role, first activating the alkyne towards nucleophilic attack and then generating the Brønsted acid required for the transformation of the alkenyl azide into the final tetrazole.We first studied the reaction of the aryl alkynes 1 a-c with TMSN 3 [16] and complex A under stoichiometric conditions. Scheme 1. Synthesis of nitriles (2) [9] and carboxamines (3) [10] from alkynes (1) by aryl-alkyne C(sp 2 )ÀC(sp) bond cleavage. DMSO = dimethylsulfoxide, TFA = trifluoroacetic acid, TMS = trimethylsilyl.Scheme 2. Mechanistic proposal for the formation of 2 and 3. [9,10] Scheme 3. Synthesis of N-aryltetrazoles (8) from alkynes (1). DCE = 1,2,-dichloroethane.

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confidence: 99%

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confidence: 99%

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confidence: 99%

“…Mechanistic proposal for the formation of 2 and 3. [9,10] Scheme 3. Synthesis of N-aryltetrazoles (8) from alkynes (1).…”

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confidence: 99%

mentioning

confidence: 99%

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Gold‐Catalyzed Synthesis of Tetrazoles from Alkynes by CC Bond Cleavage

Gaydou

Echavarren

2013

Angewandte Chemie

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Copper‐Catalyzed Oxidative Transformation of Secondary Alcohols to 1,5‐Disubstituted Tetrazoles

2014

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A mild and convenient oxidative transformation of secondary alcohols to 1,5-disubstituted tetrazoles is uncovered by employing trimethylsilyl azide (TMSN 3 ) as a nitrogen source in the presence of a catalytic amount of copper(II) perchlorate hexaA C H T U N G T R E N N U N G hydrate [CuA C H T U N G T R E N N U N G (ClO 4 ) 2 . 6 H 2 O] (5 mol%) and 2,3-dichloro-5,6-dicyano-para-benzoquinone (DDQ) (1.2 equiv.) as an oxidant. This reaction is performed under ambient conditions and proceeds through C À C bond cleavage.Keywords: alcohols; azides; copper; regioselectivity; tetrazoles Metal-mediated transformations are useful and indispensable strategies for C À C and C À heteroatom bond forming reactions in organic synthesis.[1] In addition, C À N bond forming strategies are not only challenging but have a great impetus as they provide avenues for the synthesis of biologically active and therapeutically useful heterocycles.[2] Among the heterocyles, tetrazole and its derivatives form a vital class of nitrogencontaining molecules [3] due to their well-known biological activities [4] as well as vast applications in pharmaceuticals [5a] and material sciences.[5c] Traditionally, 1,5-disubstituted tetrazoles are prepared by (i) the reaction of nitriles with alkyl or aromatic azides, [6] (ii) the reaction of ketones [7] or oximes [8] with sodium azide or hydrazoic acid and (iii) the reaction of amides [9] with sodium azide in the presence of PCl 5 or triflic anhydride, etc. Gold-catalyzed synthesis of tetrazoles using alkynes has been recently reported by Echavarren and Gaydou.[10] Recently, Jiao and coworkers developed a method to synthesize 1,5-disubstituted tetrazoles using 1,3-diphenylpropene, [11] which requires precursors that are relatively difficult to access and require multistep synthetic sequences. [12] Additionally, this protocol uses a large excess of TMSN 3 (5.5 equiv.), harsh reaction conditions (80 8C), and requires additives and long reaction times.In continuation of our investigations on the utility of azides in C À N bond forming reactions, especially leading to the formation of nitriles, [13] and in the light of Jiaos work, [11] we anticipated that secondary alcohols in the presence of a Cu salt, an excess of trimethylsilyl azide (TMSN 3 ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), may form the corresponding azide in situ and then undergo a rearrangement to form the nitrilium ion, which may be trapped in a [2+3] cycloaddition fashion by the excess azide present in the reaction medium (Scheme 1). Herein, we present our detailed investigation for converting secondary alcohols directly to 1,5-disubstituted tetrazoles in a one-pot fashion under ambient conditions. We began our study by investigating the Cu-catalyzed reaction of (E)-1,3-diphenylprop-2-en-1-ol 1a with TMSN 3 as a nitrogen source and DDQ as an oxidant (Table 1). Preliminary studies were carried out using Cu(I) and Cu(II) salts such as CuCl, CuBr, CuI, These are not the final page numbers! ÞÞ COMMUNICATIONS

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Silver‐Catalyzed Transformation of Propargylic Amine N‐Oxides to Enones and Acyloxy Ketones via Isoxazolinium Intermediates

Cui¹,

Kung²,

Ko³

et al. 2014

Adv Synth Catal

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A novel silver-catalyzed transformation of propargylic amine N-oxides with switchable product profiles has been developed. A diversity of enones with excellent E/Z ratios (up to > 20:1) were obtained when the reactions were conducted in aprotic solvents. In contrast, 3-chlorobenzoxymethyl ketones and a-(3-chloro)-benzoxy enones were obtained by using protic solvents. Mechanistic studies suggested that in situ generated isoxazolinium ions are the key intermediates involved in these novel silver-catalyzed reaction pathways. Applications on the chemoselective modification of cysteine-containing peptides in aqueous medium have also been achieved. COMMUNICATIONS Jian-Fang Cui et al. Scheme 2. A proposed reaction mechanism.

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Silver‐Catalyzed Nitrogenation of Alkynes: A Direct Approach to Nitriles through CC Bond Cleavage

Cited by 54 publications

References 105 publications

Gold‐Catalyzed Synthesis of Tetrazoles from Alkynes by CC Bond Cleavage

Gold‐Catalyzed Synthesis of Tetrazoles from Alkynes by CC Bond Cleavage

Copper‐Catalyzed Oxidative Transformation of Secondary Alcohols to 1,5‐Disubstituted Tetrazoles

Silver‐Catalyzed Transformation of Propargylic Amine N‐Oxides to Enones and Acyloxy Ketones via Isoxazolinium Intermediates

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