Synthesis of β-Amino Alcohols from Aromatic Amines and Alkylene Carbonates Using Na-Y Zeolite Catalyst

Abstract

A simple, efficient, and environmentally benign methodology for the synthesis of b-amino alcohols from aromatic amines and alkylene carbonates in the presence of the highly active and reusable solid base catalyst Na-Y zeolite is demonstrated.The synthesis of b-amino alcohols by N-alkylation of aromatic amines using alkylene carbonates is attractive due to the non-hazardous nature of alkylene carbonates. The major drawback of conventional methodology is that it involves handling of potentially hazardous epoxides 1 and the reaction is usually non-facile when poorly nucleophilic amines, such as anilines, are used. 2 In order to overcome the problem of the poor reactivity of anilines, catalysts are necessary; 2 however, these catalysts are often corrosive and costly. 3 In contrast, the alkylation employing an alkylene carbonate is easy to handle and does not require the high-pressure equipment often necessary when working with highly volatile epoxides (especially when working with ethylene oxide). 4 b-Amino alcohols are extensively used in medicinal chemistry in the preparation of biologically active natural and synthetic products, as artificial amino acids, and as chiral auxiliaries for asymmetric synthesis. 5 They are also useful as intermediates in the synthesis of perfumes, 6 hair dyes, and photo developers, 4a while oxazolidones 7 are useful in the field of biology.Although, N-alkylation and alkoxy carbonylation of amines by dimethyl carbonate to an N-alkyl amine and carbamate, respectively, is well known; 8,9 the extension of this methodology to the preparation of b-amino alcohols is not well investigated. 10 Aromatic amines are reported to react with alkylene carbonate in the presence of LiCl as a catalyst to give oxazolidones as the major product, along with b-amino alcohols. 11 Kaye et al. reported the synthesis of N-methyl-N-phenylethanolamine from N-methylaniline and ethylene carbonate using a corrosive and flammable homogeneous lithium amide catalyst. 12 It has been reported that reaction between an amine and alkylene carbonate gives polymeric products possessing carbamate and carbonate functionality. [13][14][15] The patent literature on this reaction revealed that the use of solid base catalysts such as mixed metal oxides and hydrotalcite could be effective. 16 However, these catalysts show poor activity and are not attractive from a synthetic viewpoint. Thus, there is scope to develop an efficient method for the synthesis of b-amino alcohols. To the best of our knowledge, the detailed information on this simple but useful reaction to give b-amino alcohols is not available in the literature. As a part of our ongoing program to develop green chemistry processes, we are exploring new protocols to replace toxic and hazardous reagents e.g. epoxides with alkylene carbonates, a benign reagent, to generate versatile organic molecules using heterogeneous catalysts. Interest in the use of solid base catalysts for organic synthesis is increasing because these catalysts are safe to handle, non-corrosive, low cost,...