Development of a General Non‐Noble Metal Catalyst for the Benign Amination of Alcohols with Amines and Ammonia

The N‐alkylation of amines or ammonia with alcohols is a valuable route for the synthesis of N‐alkyl amines. However, as a potentially clean and economic choice for N‐alkyl amine synthesis, non‐noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeO_x catalyst was designed and prepared for the N‐alkylation of ammonia or amines with alcohol or primary amines. N‐alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of organic ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N‐heterocyclic compounds, and secondary amines could be N‐alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one‐pot reaction of ammonia and alcohols. In addition to excellent catalytic performance, the catalyst itself possesses outstanding superiority, that is, it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixture and it could be recovered and reused for several runs without obvious deactivation.     

‘On water’: unprecedented nucleophilic substitution and addition reactions with 1,4-quinones in aqueous suspension

Unique nucleophilic substitution and addition reactions of 1,4-quinones in aqueous suspension with aromatic amines, primary aliphatic amines, amino acid, ester of amino acid, heterocyclic amines, hydrazine, amide, and thioethers are described in absence of catalyst against the traditional synthetic routes of these reactions in non-aqueous medium in presence of catalyst.     

Colloid and nanodimensional catalysts in organic synthesis: III. Alkylation of amines with primary alcohols catalyzed by colloidal nickel and cobalt

Alkylation of primary amines with primary alcohols has been performed under catalysis by colloidal nickel and cobalt particles. The synthesis of the catalyst and alkylation of amines have been carried out in a one-pot mode. The alkylation at 160–180°C in 6–12 h yields 55–90% of secondary amines.     

Selective hydroaminomethylation of olefins using simple and efficient Rh–phosphinite complex catalyst

Hydroaminomethylation of various olefins with primary and secondary amines was carried out using a simple and efficient rhodium–phosphinite complex catalyst. The influence of various reaction parameters including the effects of temperature, pressure, catalyst loading, time and solvents has been investigated. The present protocol is general with wider substrate applicability for the synthesis of an important class of aliphatic amines and arylethylamines. High activity and selectivity for amines was achieved with a very good substrate/catalyst molar ratio (turnover number 2500) under mild reaction conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly reactive, general and long-lived catalysts for palladium-catalyzed amination of heteroaryl and aryl chlorides, bromides, and iodides: scope and structure-activity relationships

We describe a systematic study of the scope and relationship between ligand structure and activity for a highly efficient and selective class of catalysts containing sterically hindered chelating alkylphosphines for the amination of heteroaryl and aryl chlorides, bromides, and iodides. In the presence of this catalyst, aryl and heteroaryl chlorides, bromides, and iodides react with many primary amines in high yields with part-per-million quantities of palladium precursor and ligand. Many reactions of primary amines with both heteroaryl and aryl chlorides, bromides, and iodides occur to completion with 0.0005-0.05 mol % catalyst. A comparison of the reactivity of this catalyst for the coupling of primary amines at these loadings is made with catalysts generated from hindered monophosphines and carbenes, and these data illustrate the benefits of chelation. Studies on structural variants of the most active catalyst indicate that a rigid backbone in the bidentate structure, strong electron donation, and severe hindrance all contribute to its high reactivity. Thus, these complexes constitute a fourth-generation catalyst for the amination of aryl halides, whose activity complements catalysts based on monophosphines and carbenes.     

High performance of nitrogen-doped carbon-supported cobalt catalyst for the mild and selective synthesis of primary amines

A nitrogen-doped carbon-supported Co catalyst (Co/N-C-800) was discovered to be highly active for the reductive amination of carbonyl compounds with NH₃ and the hydrogenation of nitriles into primary amines using H₂ as the hydrogen source. Structurally diverse carbonyl compounds were selectively transformed into primary amines with good to excellent yields (82.8–99.6%) under mild conditions. The Co/N-C-800 catalyst showed comparable or better catalytic performance than the reported noble metal catalysts. The Co/N-C-800 catalyst also showed high activity for the hydrogenation of nitriles, affording the corresponding primary amines with high yields (81.7–99.0%). An overall reaction mechanism is proposed for the reductive amination of benzaldehyde and the hydrogenation of benzonitrile, which involves the same intermediates of phenylmethanimine and N-benzylidenebenzylamine.     

Chemoselective organocatalytic aerobic oxidation of primary amines to secondary imines

Biomimetic aerobic oxidation of primary benzylic amines has been achieved by using a quinone catalyst. Excellent selectivity is observed for primary, unbranched benzylic amines relative to secondary/tertiary amines, branched benzylic amines, and aliphatic amines. The exquisite selectivity for benzylic amines enables oxidative self-sorting within dynamic mixtures of amines and imines to afford high yields of cross-coupled imine products.     

Intramolecular hydroamination of aminoalkenes catalyzed by a cationic zirconium complex

A new cationic [N(-)O(-)S]zirconium complex (cat.) was developed to be an excellent catalyst for the intramolecular hydroamination of aminoalkenes with a large substrate scope from terminal alkenes to internal alkenes, and primary amines to secondary amines. The catalyst system can also tolerate various functional groups and perform sequential hydroamination of primary aminodienes.     

The synthesis of amines by the homogeneous hydrogenation of secondary and primary amides

Amides can be hydrogenated to amines using a catalyst prepared in situ from [Ru(acac)(3)] and 1,1,1-tris(diphenylphosphinomethyl)ethane; water is required to stabilize the catalyst and primary amines can only be formed (selectivity up to 85%) if ammonia is also present.     

Nickel-NHC-catalyzed alpha-arylation of acyclic ketones and amination of haloarenes and unexpected preferential N-arylation of 4-aminopropiophenone

Arylation of both acyclic ketones and primary and secondary amines was achieved using a new, simple, stable, and easy-to-access nickel(II)-halide complex bearing mixed PPh3/N-heterocyclic carbene ligands as a catalyst precursor. Acyclic ketones were first arylated at the alpha-position with the nickel catalyst. On the other hand, less basic amines, such as diphenylamine and 4-aminobenzophenone, were more favorable in the catalytic amination of haloarenes than basic amines, contrary to previous reports. N-Arylation of 4-aminopropiophenone was found to proceed selectively without causing alpha-arylation of the ketone group.     

Chemoselective hydrogenation of nitriles to primary amines catalyzed by water‐soluble transition metal catalysts

The water‐soluble rhodium complex generated in situ from [Rh (COD)Cl]₂ in aqueous ammonia has been revealed as a highly efficient catalyst for the hydrogenation of aromatic nitriles, to primary amines with excellent yields. The catalyst is also highly selective towards primary amines in the case of sterically hindered aliphatic nitriles. The catalytic system can also be recycled and re‐used with no significant loss of activity.     

First iron-catalyzed guanylation of amines: a simple and highly efficient protocol to guanidines

The first iron-catalyzed guanylation of amines is reported. Commercially available Fe(OAc)₂ acts as an excellent catalyst for the addition of amines to carbodiimides. The reaction is broadly applicable to a variety of primary, secondary, and heterocyclic amines, and tolerates a wide range of functionalities allowing the easy preparation of a large family of guanidines. The low price and low toxicity of the commercially available iron catalyst make this methodology highly attractive.     

CuI/DMPAO-catalyzed N-arylation of acyclic secondary amines

DMPAO has been found to be a powerful ligand to enable copper-catalyzed coupling of aryl halides with aliphatic acyclic secondary amines take place under relatively mild conditions, and coupling of aryl halides with primary amines and cyclic secondary amines proceeds at low catalyst loading.     

Efficient catalyst-free chemical fixation of carbon dioxide into 2-oxazolidinones under supercritical condition

4-Methylene-1,3-oxazolidin-2-ones can be synthesized from propargylic alcohols,primary amines and carbon dioxide under supercritical condition in the absence of any additional catalyst and solvent.Various propargylic alcohols and primary amines were examined.     

Dynamic kinetic resolution of primary amines with a recyclable Pd nanocatalyst for racemization

A practical procedure for the dynamic kinetic resolution (DKR) of primary amines has been developed. This procedure employs a palladium nanocatalyst as the racemization catalyst, a commercial lipase (Novozym-435) as the resolution catalyst, and ethyl acetate or ethyl methoxyacetate as the acyl donor. Eleven primary amines and one amino acid amide have been efficiently resolved with good yields (85-99%) and high enantiomeric excesses (97-99%). [reaction: see text]     

Study of CuI catalyzed coupling reactions of aryl bromides with imidazole and aliphatic amines under microwave dielectric heating

Amination of a variety of functionalized aryl bromides with imidazole and primary and secondary amines was accomplished using a CuI/amino acid catalyst system under microwave heating. Application of microwave irradiation shortened the reaction time from 25–40 h to 6–20 min. Good to very good yields of the corresponding coupling products were obtained when imidazole and secondary amines were used as starting materials. In case of primary amines, the outcome of the reaction was dependent on the character of the substituent on aryl bromide.     

Reductive Amination of Carbonyl Compounds with Ammonia and Hydrogenation of Nitriles to Primary Amines with Heterogeneous Cobalt Catalysts

Reductive amination of aldehydes/ketones with aqueous NH3 and hydrogenation of nitriles to primary amines with Co catalysts were reported. Co@NC-700 exhibited remarkable activity and high selectivity for the reductive amination of aldehydes/ketones with aqueous NH3 and the hydrogenation of nitriles to primary amines. Several primary amines can be obtained with good to excellent yields via the reductive amination of aldehydes/ketones and the hydrogenation of nitriles. The nitrogen-doped carbon(C)-supported Co@NC-700 metal catalyst was prepared via the pyrolysis of bioMOF Co/adenine in activated C. Co@NC-700 can be reused five times without evident loss of activity.     

Formylation of amines through catalyst- and solvent-free transamidation reaction

The transamidation between formamide and various amines proceeds under heating, without any catalyst nor solvent, providing thus green and neutral conditions for the formylation of primary and secondary amines. The resulting amide product can be directly transformed, in a one pot sequence, into monomethylamine.     

Primary Amines by Transfer Hydrogenative Reductive Amination of Ketones by Using Cyclometalated IrIII Catalysts

Cyclometalated iridium complexes are found to be versatile catalysts for the direct reductive amination (DRA) of carbonyls to give primary amines under transfer‐hydrogenation conditions with ammonium formate as both the nitrogen and hydrogen source. These complexes are easy to synthesise and their ligands can be easily tuned. The activity and chemoselectivity of the catalyst towards primary amines is excellent, with a substrate to catalyst ratio (S/C) of 1000 being feasible. Both aromatic and aliphatic primary amines were obtained in high yields. Moreover, a first example of homogeneously catalysed transfer‐hydrogenative DRA has been realised for β‐keto ethers, leading to the corresponding β‐amino ethers. In addition, non‐natural α‐amino acids could also be obtained in excellent yields with this method.     

A highly chemoselective Boc protection of amines using sulfonic-acid-functionalized silica as an efficient heterogeneous recyclable catalyst

A facile and versatile method for the chemoselective Boc protection of amines has been developed by a treatment with (Boc)₂O in the presence of sulfonic-acid-functionalized silica as a catalyst. The method is general for the preparation of N-Boc derivatives of aliphatic (acyclic and cyclic), aromatic, and heteroaromatic amines; primary and secondary amines; aminols, amino-esters; and sulfonamides. The catalyst works under heterogeneous conditions and can be recycled.