Abstract
This study presents a simple highly versatile and efficient synthesis of various β-amino carbonyl compounds in the Mannich reaction of acetophenone with aromatic aldehydes and aromatic amines in the presence of nanosulfated zirconia, nanostructured ZnO, nano-γ-alumina, and nano-ZSM-5 zeolites as the catalyst in ethanol at moderate temperature. The optical properties of the nanostructured organic molecules were studied. The advantages of methods are short reaction times, milder conditions, easy workup, and purification of products by nonchromatographic methods. The catalysts can be recovered for the subsequent reactions and reused without any appreciable loss of efficiency.
Highlights
IntroductionThe Mannich reaction is a classical method for the preparation of b-amino ketones and aldehydes[1,2,3] and has been one of the most important basic reactions in organic synthesis because it affords synthetically and biologically important b-amino carbonyl compounds that are important intermediates for the construction of various nitrogen-containing amino alcohols, peptides, lactams, optically active amino acids, natural products, and pharmaceuticals.[4,5,6,7,8,9,10,11,12,13,14,15,16,17,18] Due to the drastic reaction conditions, severe side reactions, substrate limitations, expensive reagents or catalysts, and the long reaction time and low yield, the classical intermolecular Mannich reaction is plagued by a number of serious disadvantages.[19,20,21] To overcome the drawbacks of the classic method, the Lewis acid catalyzed condensation of ketone to preformed imines is an excellent variant of the Mannich reaction.[22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]there is high interest in developing convenient methods for the synthesis of b-amino ketones
As a part of our continuing effort toward the development of useful synthetic methodologies,[93] we report an efficient process for synthesis of various b-amino carbonyl compounds in the Mannich reaction of acetophenone with aromatic aldehydes and aromatic amines using nanostructured
We compared the results of b-amino carbonyl compounds synthesis from acetophenone, benzaldehyde, and aniline with the presence of nanostructured ZnO, nanosulfated zirconia, nano-g-alumina, and nano-ZSM-5 zeolites as the catalyst (Table 1)
Summary
The Mannich reaction is a classical method for the preparation of b-amino ketones and aldehydes[1,2,3] and has been one of the most important basic reactions in organic synthesis because it affords synthetically and biologically important b-amino carbonyl compounds that are important intermediates for the construction of various nitrogen-containing amino alcohols, peptides, lactams, optically active amino acids, natural products, and pharmaceuticals.[4,5,6,7,8,9,10,11,12,13,14,15,16,17,18] Due to the drastic reaction conditions, severe side reactions, substrate limitations, expensive reagents or catalysts, and the long reaction time and low yield, the classical intermolecular Mannich reaction is plagued by a number of serious disadvantages.[19,20,21] To overcome the drawbacks of the classic method, the Lewis acid catalyzed condensation of ketone to preformed imines is an excellent variant of the Mannich reaction.[22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]there is high interest in developing convenient methods for the synthesis of b-amino ketones. Direct Mannich reactions of aldehydes, ketones, and aryl amines have been realized via HCl,[41,42,43] Lewis acids,[44,45,46,47,48,49,50,51,52,53,54,55] praline,[56,57,58] p-dodecyl benzene sulfonic acid,[59] PS-SO3H (polymer-support sulfonic acid),[60] lanthanides,[61,62] transition metal salt catalysis,[63] organocatalytic approaches,[64,65,66] Yb(OiPr)[3,67] InCl3,68,69 BiCl3,70 phosphorodiamidic acid,[71] AuCl3–PPh3,72 iodine,[73] aluminum nitrate,[74] sulfamic acid,[75] ceric ammonium nitrate (CAN),[76] salen–Zn complex,[77] rare-earth metal triflates,[78,79,80] NbCl5,81 Zn(OTf)[2,82] samarium(II) iodide,[83] Nano-TiO2,84 and silicasupported AlCl3.85 Various other promoters, such as Bronsted acid catalysts,[86,87] have been reported to catalyze the Mannich reaction
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