At 140 ◦C, in the presence of alkali metal exchanged faujasites, preferably NaY, as catalysts, glycerine carbonate (GlyC) is an efficient and green alkylating agent of primary aromatic amines (p-XC6H4NH2, X = H, OMe, OH, Cl): the reaction takes place with a high conversion (~90%) and a good selectivity (80–90%) for the formation of N-(2,3-dihydroxy)propyl anilines (p-XC6H4NHCH2CH(OH)CH2OH). The alkylation process does not proceed through an exclusive nucleophilic substitution of anilines at the C5 position of GlyC. Evidence proves that a dehydrative condensation of anilines with GlyC produces intermediate species, and both transesterification and hydrolysis reactions are involved to obtain the final N-alkyl derivatives. A mechanism is proposed accordingly. Experiments show that faujasites are recyclable catalysts on condition that they are exposed to a mild thermal activation (70 ◦C, 18 mbar) prior to their re-use. Otherwise, if zeolites are calcined (400 ◦C, air), both the catalyst activity and the reaction selectivity drop. Isolated yields (60–65%) of N-(2,3-dihydroxy)propyl anilines are somewhat limited by the difficult separation of the unreacted GlyC and of the by-product glycerine. Nonetheless, the overall efficiency of the method is comparable to that of alternative routes based on highly toxic reagents (glycidol and aryl halides).

The Reaction of Glycerol Carbonate with Primary Aromatic Amines in the Presence of Y- and X-Faujasites: the Synthesis of N-(2,3-dihydroxy)propyl anilines and the Reaction Mechanism

SELVA, Maurizio;FABRIS, Massimo
2009-01-01

Abstract

At 140 ◦C, in the presence of alkali metal exchanged faujasites, preferably NaY, as catalysts, glycerine carbonate (GlyC) is an efficient and green alkylating agent of primary aromatic amines (p-XC6H4NH2, X = H, OMe, OH, Cl): the reaction takes place with a high conversion (~90%) and a good selectivity (80–90%) for the formation of N-(2,3-dihydroxy)propyl anilines (p-XC6H4NHCH2CH(OH)CH2OH). The alkylation process does not proceed through an exclusive nucleophilic substitution of anilines at the C5 position of GlyC. Evidence proves that a dehydrative condensation of anilines with GlyC produces intermediate species, and both transesterification and hydrolysis reactions are involved to obtain the final N-alkyl derivatives. A mechanism is proposed accordingly. Experiments show that faujasites are recyclable catalysts on condition that they are exposed to a mild thermal activation (70 ◦C, 18 mbar) prior to their re-use. Otherwise, if zeolites are calcined (400 ◦C, air), both the catalyst activity and the reaction selectivity drop. Isolated yields (60–65%) of N-(2,3-dihydroxy)propyl anilines are somewhat limited by the difficult separation of the unreacted GlyC and of the by-product glycerine. Nonetheless, the overall efficiency of the method is comparable to that of alternative routes based on highly toxic reagents (glycidol and aryl halides).
2009
11
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10278/29826
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