Benzylation Of Amines Research Articles

Iridium complexes with a new type of N^N′‐donor anionic ligand catalyze the N‐benzylation of amines via borrowing hydrogen

The development of efficient and eco‐friendly methods for the synthesis of elaborate amines is highly desired as they are valuable chemicals. The catalytic alkylation of amines using alcohols as alkylating agents, through the so‐called borrowing hydrogen process, satisfies several of the principles of green chemistry. In this paper, four neutral half‐sandwich complexes of Ru(II), Rh(III), and Ir(III) have been synthesized and tested as catalysts in the N‐benzylation of amines with benzyl alcohol. The new derivatives contain a N^N′ anionic ligand derived from 5‐(pyridin‐2‐ylmethylene)hydantoin (Hpyhy) that has never been tested in metal complexes with catalytic applications. In particular, the Ir derivatives, [(Cp*)IrX(pyhy)] (X = Cl or H), exhibit high activity along with good selectivity in the process. Indeed, the scope of the optimized protocol has been proved in the benzylation of several primary and secondary amines. The selectivity towards monoalkylated or dialkylated amines has been tuned by adjusting the amine:alcohol ratio and the reaction time. Experimental results support a mechanism consisting of three consecutive steps, two of which are Ir catalyzed, and a favorable condensation step without the assistance of the catalyst. Moreover, an unproductive competitive pathway can operate when the reaction is performed in open‐air vessels, due to the irreversible release of H2. This route is hampered when the reaction is carried out in close vessels, likely because the release of H2 is reversed through metal‐based heterolytic cleavage. From our viewpoint, these results show the potential of the new catalysts in a very attractive and promising methodology for the synthesis of amines.

SiO2-Cu2O: An efficient and recyclable heterogeneous catalyst for N-benzylation of primary and secondary amines

A mild, effective, and selective procedure is reported for the mono N -benzylation and N , N -dibenzylation of primary amines as well as mono N -benzylation of secondary amines using silica-supported copper(I) oxide in water. The silica-supported Cu 2 O was generated in situ by the reaction of Fehling solution and glucose at 100 °C onto activated silica. The catalyst was filtered, washed with water, and oven-dried, and was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic absorption spectroscopy. The prepared Cu 2 O-SiO 2 was found to be thermally stable up to 325 °C. The copper was uniformly distributed onto the surface of the silica, and the mean particle diameter was 7 nm. The catalyst served as a selective heterogenous catalyst for the N -benzylation of primary and secondary amines. The catalyst is recyclable and was used effectively upto fifth run without a significant loss of catalytic activity. Various reaction solvents including water, acetonitrile, and toluene were screened for N -benzylation of amines, and the success of the aqueous system highlights the low environmental impact of the procedure. Silica-supported Cu 2 O was prepared in situ using inexpensive and widely available starting materials and used as a catalyst for N -benzylation and N , N -dibenzylation of primary and secondary amines.

New Heteroaromatic Azo Compounds Based on Pyridine, Isoxazole, and Benzothiazole for Efficient and Highly Selective Amidation and Mono-N-Benzylation of Amines under Mitsunobu Conditions

4,4′-Azopyridine (2c) is used in conjunction with triphenylphosphine for the efficient conversion of carboxylic acids into amides via Mitsunobu reaction with primary and secondary aliphatic and aro...

5. The benzylation of amines. Part IV. The rate of reaction of benzyl bromide with nitrobenzylaniline and some derivatives

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The Velocity Coefficient for Bimolecular Reactions in Solution

IN a letter under the above title in NATURE of May 12, the interchange of energy between solvent and dissolved reactant molecules is discussed. This matter was considered in a paper entitled “The Benzylation of Amines: Part 3,” in the Journal of Physical Chemistry, 673; 1926. If activated molecules of solute are deactivated by collision with solvent molecules, the latter molecules may either acquire a higher velocity, or be themselves activated, or radiation may be emitted, for the energy absorbed from the activated solute must go somewhere. The molecules of the solvent cannot acquire a higher velocity unless the temperature of the solution rises. I do not know whether there is any experimental evidence in support of this; what it amounts to in a simple case appears to be that if we isolate two vessels, one containing, say, benzene, and the other a solution of a reacting substance such as benzyl bromide in benzene, then the temperature of the latter should rise. If the reply is that unactivated molecules of the reactant absorb this energy of translation of the solute molecules, then the position is as suggested by Mr. Louis Kassel (NATURE, May 12), namely, that the effect of the third molecule, the solvent, should probably be as often activational as deactivational.

The Benzylation of Amines. III

The Benzylation of Amines. III