Borane-Catalyzed Chemoselectivity-Controllable N-Alkylation and <i>ortho</i> C-Alkylation of Unprotected Arylamines Using Benzylic Alcohols

Meng, Shan‐Shui; Tang, Xiaowen; Luo, Xiang; Wu, Ruibo; Zhao, Junling; Chan, Albert S. C.

doi:10.1021/acscatal.9b03038

Cited by 53 publications

(25 citation statements)

References 66 publications

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“…Methanol was detected in the experiment, which may be the byproduct of the C−H/C−O coupling. Previous study had revealed a C ‐alkylation reaction between aniline and benzylic alcohols catalyzed by B(C 6 F 5 ) 3 in the presence of 1,1,1,3,3,3‐hexafluoro‐2‐propanol . No similar C ‐alkylations reaction between methanol and N,N‐Dialkylanilines were observed in our experiment.…”

Section: Optimization Of Reaction Conditions[a]contrasting

confidence: 55%

B(C₆F₅)₃‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines

Zhai

Liu

et al. 2020

Chemistry An Asian Journal

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Tandem Friedel-Crafts (FC) and CÀ H/CÀ O coupling reactions catalyzed by tris(pentafluorophenyl) borane (B (C 6 F 5) 3) were achieved without using any other additive in the absence of solvent. This process can be used for the reactions between a series of dialkylanilines and vinyl ethers with good isolated yields of bis(4-dialkylaminophenyl) compounds. Based on combined theoretical and experimental studies, the possible reaction mechanism was proposed. B(C 6 F 5) 3 can activate the C=C and CÀ O bond for FC and CÀ H/CÀ O coupling reactions respectively. The FC reaction is slow, which is followed by a fast CÀ H/CÀ O coupling. Constructing CÀ C bond is one of the most important topics in both academic laboratories and industrial production. Many famous reactions have been developed for the CÀ C bond formation. [1] Among them, CÀ H/CÀ O coupling and Friedel-Crafts (FC) reactions are two effective strategies. [2-13] Both CÀ H and CÀ O bonds are quite inert. Hence, the CÀ H/ CÀ O coupling to produce CÀ C bond is full of challenges. Until now, effectively accessing this coupling reaction still requires metal-based catalysts, [2] such as compounds containing Ni, [3] Fe, [4] Co, [5] Mn [6] , Rh, [7] Ir, [8] or Pd. [9] It is worth noticing that, besides the use of highly active metal-based catalysts, some of these reported CÀ H/CÀ O coupling reactions also require preactive substrates, such as Grignard reagent, [3a,m, n, 4] organolithium reagent, [3i,q] or organoboron compound. [3b,j, r, 9] Though FC reactions have been widely used to introduce CÀ C bond on aromatic ring, [10] this reaction is usually unsuitable for alkalinous substrates due to the coordination of the amines to these reported acid catalysts. Classical textbook especially emphasizes the incompatibility of FC reactions to amines. [11] For N-containing substrates, great achievements have been obtained for the FC reactions of indole and pyrrole because of the extremely weak alkalinity of these two compounds. [12] However, the FC reactions become challenging for substrates with enhanced alkalinity, such as dialkylanilines. Recently, Bertrand and we achieved the FC reaction of dialkylanilines by using carbene-gold (I) as catalyst. [13] Now, more and more substrates with alkalinity have been successfully used for FC reactions. [14] It is worth noticing that the reported catalysts of the CÀ H/ CÀ O couplings [3-9] are quite different from those of FC [a]

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Section: Optimization Of Reaction Conditions[a]contrasting

confidence: 55%

B(C₆F₅)₃‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines

Zhai

Liu

et al. 2020

Chemistry An Asian Journal

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“…Meanwhile, transition metal‐catalyzed N‐alkylation reaction of amines using alcohol as an alkylating agent via borrowing hydrogen or hydrogen autotransfer method has emerged as an excellent alternative and environmentally‐benign approach in organic synthesis . Notably, the use of alcohol as the alkylating agent makes the reaction greener as it affords only water as the byproduct . Mechanistically, the reaction proceeds via dehydrogenation of alcohol, giving carbonyl compound, which then undergoes reaction with a nucleophile such as an amine to give imine.…”

Section: Introductionmentioning

confidence: 99%

Zinc‐Catalyzed N‐Alkylation of Aromatic Amines with Alcohols: A Ligand‐Free Approach

et al. 2020

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An efficient zinc-catalyzed N-alkylation reaction of aromatic amines was achieved using aliphatic, aromatic, and heteroaromatic alcohols as the alkylating reagent. A variety of aniline derivatives, including heteroaromatic amines, underwent the N-alkylation reaction and furnished the corresponding monoalkylated products in good to excellent yields. The application of the reaction is also further demonstrated by the synthesis of a 2-phenylquinoline derivative from acetophenone and 2-aminobenzyl alcohol. Deuterium labeling experiments show that the reaction proceeds via a borrowing hydrogen process.

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“…[68] In 2019, Chan and co-workers showed that electron-rich primary anilinesu ndergo selective N-alkylation in nitromethane with ar ange of secondary andt ertiaryb enzylic alcohols catalysed by BCF 4 (10 mol %). [9] Subsequently,M aji disclosed the BCF 4 (1 mol %) promoted dehydrative alkylation of secondary anilines with ar ange of electron-rich primary,s econdary or tertiary benzylic alcohols. [69] The method was also applicable to the monoalkylation of primary sulfonamides.…”

Section: Dehydrative Cànb Ond Formationmentioning

confidence: 99%

“…Meng and co‐workers have subsequently used the same catalyst for the Friedel–Crafts alkylation of phenols with a variety of secondary benzylic alcohols [8] . The same group has extended this to the BCF 4 (10 mol %) catalysed Friedel–Crafts alkylation of electron‐rich anilines with secondary benzylic alcohols [9] . The process is highly solvent dependent, with selective C ‐alkylation observed in hexafluoroisopropanol (HFIP) and N ‐alkylation observed in nitromethane.…”

Section: Dehydrative C−c Bond Formationmentioning

confidence: 99%

Brønsted Acid‐Catalysed Dehydrative Substitution Reactions of Alcohols

Estopiñá-Durán

Taylor

2020

Chemistry A European J

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Borane-Catalyzed Chemoselectivity-Controllable N-Alkylation and ortho C-Alkylation of Unprotected Arylamines Using Benzylic Alcohols

Cited by 53 publications

References 66 publications

B(C₆F₅)₃‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines

B(C₆F₅)₃‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines

Zinc‐Catalyzed N‐Alkylation of Aromatic Amines with Alcohols: A Ligand‐Free Approach

Brønsted Acid‐Catalysed Dehydrative Substitution Reactions of Alcohols

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Borane-Catalyzed Chemoselectivity-Controllable N-Alkylation and ortho C-Alkylation of Unprotected Arylamines Using Benzylic Alcohols

Cited by 53 publications

References 66 publications

B(C6F5)3‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines

B(C6F5)3‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines

Zinc‐Catalyzed N‐Alkylation of Aromatic Amines with Alcohols: A Ligand‐Free Approach

Brønsted Acid‐Catalysed Dehydrative Substitution Reactions of Alcohols

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B(C₆F₅)₃‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines

B(C₆F₅)₃‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines