Highly Efficient and Selective Catalytic <i>N</i>‐Alkylation of Amines with Alcohols in Water

Norinder, Jakob; Börner, Armin

doi:10.1002/cctc.201100197

Cited by 30 publications

(11 citation statements)

References 68 publications

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“…With water-soluble and air-stable iridium-amine complex [Cp*Ir(NH 3 ) 3 ]I 2 (102) as the catalyst, various secondary and tertiary amines were synthesized by the N-alkylation reactions of theoretical equivalents of amines and alcohols in water without a base under air. 117,118 In this case, versatile alcohols and amines were employed to undergo the BH-type reactions, giving the target higher-order amine products (eqn (37)). (37) N-Alkylation of poor nucleophilic sulfonamides with alcohols was performed in water by means of a water-soluble iridium complex {Cp*Ir[6,6 0 -(OH) 2 -bpy](H 2 O)}(OTf) 2 .…”

Section: Substitution Of Alcohols By N-nucleophiles In the Aqueous Phasementioning

confidence: 99%

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

2015

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Transition metal-catalyzed substitution of alcohols by N-nucleophiles (or N-alkylation of amines and related compounds with alcohols) avoids the use of alkylating agents by means of borrowing hydrogen (BH) activation of the alcohol substrates. Water is produced as the only by-product, which makes the "BH" processes atom-economic and environmentally benign. Diverse types of homogeneous organometallic and heterogeneous transition metal catalysts, and substrates such as N-nucleophiles including amines, amides, sulfonamides and ammonia, and various alcohols, can be used for this purpose, demonstrating the promising potential of "BH" processes to replace the procedures using traditional alkylating agents in pharmaceutical and chemical industries. Borrowing hydrogen activation of alcohols for C-N bond formation has recently been paid more and more attention, and a lot of new and novel procedures and examples have been documented. This critical review summarizes the recent advances in "BH" substitution of alcohols by N-nucleophiles since 2009. "Semi-BH" N-alkylation processes with or without an external hydrogen acceptor are also briefly presented. Suitable discussion of the "BH" strategy provides new principles for establishing green processes to replace the relevant traditional synthetic methods for C-N bond formation.

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Section: Substitution Of Alcohols By N-nucleophiles In the Aqueous Phasementioning

confidence: 99%

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

2015

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“…This catalysis has attracted a great deal of attention in recent years as an environmentally benign process of synthesizing amines, which produces water as the sole byproduct . While both heterogeneous and homogeneous catalysts have been known to promote the reaction, ruthenium − and iridium − complexes have constituted a vast majority of the homogeneous catalysts because of their relatively high catalytic performance with high product selectivity . We have found that complex 1 exhibits catalytic activity comparable to that of those complexes.…”

Section: Introductionmentioning

confidence: 99%

A Bis(phosphaethenyl)pyridine Complex of Iridium(I): Synthesis and Catalytic Application to N-Alkylation of Amines with Alcohols

2013

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The iridium(I) complex [IrCl(BPEP-H)] (1), coordinated with 2,6-bis[2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyl]pyridine (BPEP-H) as a PNP-pincer-type phosphaalkene ligand, has been synthesized and fully characterized by elemental analysis, NMR spectroscopy, and X-ray diffraction analysis. Complex 1 (1 mol %) catalyzes N-alkylation of primary and secondary amines with alcohols, leading to the selective formation of secondary and tertiary amines, respectively. Primary amines are smoothly alkylated with a variety of benzylic and aliphatic alcohols (1 or 3 equiv) at 100 °C under basic conditions (CsOH, 10 mol %) to give the corresponding secondary amines in good to high yields. On the other hand, N-alkylation of secondary amines with benzyl alcohol (3 equiv) proceeds in the presence of KH2PO4 (5 mol %) at 140 °C to afford tertiary amines in high yields.

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“…Although this result could be considered as an appreciable achievement in comparison with the original discovery, from a preparative point of view, the use of tertiary amines as substrates is limited by their low availability and by the expected different selectivity in the transferred group when non-symmetrical tertiary amines are employed. [19] As exemplified in Scheme 2, a possible additional interesting aspect may be the use of o-phenylenediamine 3 in conjunction with Pd/C to transform a tertiary amine (such as 11) into a secondary one (14), a process that is still difficult to carry out. [26] Supported by the results of Table 1, o-phenylenediamine 3 was subjected to cyclization using dibutylamine (15) and even butylamine (16) obtaining a satisfactory conversion into 2-propylbenzimidazole 12 (Scheme 3).…”

Section: Resultsmentioning

confidence: 99%

“…The oxidized form (sometimes unstable by itself) is further treated with other reagents and the produced hydrogen molecule is charged on the acceptor compound (generally organic) in order to shift the reaction and regenerate the catalyst. Catalytic amination of alcohols, [13] synthesis of tertiary amines, [14] imines or amides [15,16] are the most explored transformations and homogeneous transition metals have been widely employed as the catalysts. Although in some cases acceptable TON values have been reached, [17] the catalysts are often expensive {e.g., (Cp* 4 A C H T U N G T R E N N U N G (m-H)} and require the use of ligands, introducing additional troubles for product isolation.…”

Section: Introductionmentioning

confidence: 99%

A General Approach to Substituted Benzimidazoles and Benzoxazoles via Heterogeneous Palladium‐Catalyzed Hydrogen‐Transfer with Primary Amines

et al. 2012

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The synthesis of benzimidazoles starting from o-phenylenediamines and amines in the presence of palladium on charcoal as catalyst is reported. Under microwave dielectric heating it is possible to use a tertiary, a secondary, and even a primary amine as the substrate for a palladium-mediated process to get 2-substituted or 1,2-disubstituted benzimidazoles, depending on the nature of the o-phenylenediamine employed. Primary amines are the most suitable reagents for the atom economy of the overall process that resulted to be general as several different substituted benzimidazoles were obtained in good yield. Benzoxazoles can be also prepared starting from primary amines and o-aminophenol. The reaction is also highly selective as no (poly)-alkylated pheny-A C H T U N G T R E N N U N G lenediamines or cross-contaminated benzimidazoles are obtained starting from N-monoalkylphenylenediamines. This behavior was interpreted as a scarce aptitude to dehydrogenation of the methylene bonded to the aromatic NH of N-alkylarylamines. The experiments carried out consent to draw an almost complete picture of the reaction pathways occurring during the process. The catalyst can be recycled several times and, although far from optimal performances, catalyst TON = 90 is encouraging for further large-scale optimization protocols. In addition, the palladium on charcoal-catalyzed microwave-assisted reaction of o-phenylenediamine gives de-alkylation of tertiary amines and transformation into the secondary ones.

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Highly Efficient and Selective Catalytic N‐Alkylation of Amines with Alcohols in Water

Abstract: Getting fresh with iridium: Water is the solvent of choice in the N‐alkylation of amines with iridium catalysts. Numerous secondary and tertiary amines can be assembled with excellent yields and chemoselectivity.

Cited by 30 publications

References 68 publications

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

A Bis(phosphaethenyl)pyridine Complex of Iridium(I): Synthesis and Catalytic Application to N-Alkylation of Amines with Alcohols

A General Approach to Substituted Benzimidazoles and Benzoxazoles via Heterogeneous Palladium‐Catalyzed Hydrogen‐Transfer with Primary Amines

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