Abstract
It is of great significance to develop sustainable processes of catalytic reaction. We report a selective procedure for the synthesis of acetylated bioactive compounds in water. The use of 1-acetylimidazole combined with Er(OTf)3 as a Lewis acid catalyst gives high regioselectivity and good yields for the acetylation of primary hydroxyl groups, as well as amino groups. The protection is achieved in short reaction times under microwave irradiation, and is successful even in the case of base-sensitive substrates.
Highlights
Protecting strategies are of critical importance in synthetic chemistry and represent important tools for industrial biotechnology
Synthesis [50] and “on water” reactions [42,51], we decided to test the potential use of MW in the regioselective acetylation reaction of alcohols and amino groups using 1-acetylimidazole as acetylating agent, and replacing the basic catalyst proposed by Pey et al [35] with an eco-friendly Lewis acid catalyst like Er(OTf
The reaction showed high selectivity for the acetylation of the primary hydroxyl groups in carbohydrates and diols; in the case of nucleosides, the acetylation reaction led to the formation of the 50 -O-acetyl derivative
Summary
Protecting strategies are of critical importance in synthetic chemistry and represent important tools for industrial biotechnology. Imidazole carbamates and ureas have been successfully applied in the conversion of aliphatic and aromatic carboxylic acids into esters and amides in 70–93% yields [14]. In this endeavor, Sarpong et al have reported the selective acetylation of indoles and oxazolidinones by using several reactive N-acyl imidazoles and/or carbamates; the reaction shows a high selectivity at the nitrogen atom of the non-nucleophilic azacycles, even in the presence of other strong nucleophiles, such as amines or hydroxyl groups [15]. The reaction, conducted at room temperature in acetonitrile for about 24 h, Catalysts 2017, 7, 269; doi:10.3390/catal7090269 www.mdpi.com/journal/catalysts
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