<span style="font-size:11.0pt;mso-bidi-font-size: 10.0pt;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language:AR-SA" lang="EN-GB">Chitosan biohydrogel beads: A recyclable, biodegradable, heterogeneous catalyst for the regioselective synthesis of 5-aryl-2-oxazolidinones from carbon dioxide and aziridines at mild conditions</span>

Abstract

<span style="mso-bidi-font-size:9.0pt;color:black; letter-spacing:-.1pt" lang="EN-GB">In the search for efficient catalysts for a reaction under mild conditions, c<span style="mso-bidi-font-size:9.0pt; letter-spacing:-.1pt" lang="EN-GB">ycloaddition reactions of carbon dioxide with various aziridines catalyzed by chitosan biohydrogel beads without additional solvent and metal co-catalyst to form five-membered 5-aryl-2-oxazolidinones in high yields and selectivity has been studied. Reaction rate, conversion and selectivity are studied as a function of a series of input variables including catalyst loading, temperature, pressure and solvent system. The catalyst is easily recovered and has been reused in five consecutive cycles without any significant loss of its catalytic activity and selectivity. The catalyst, chitosan biohydrogel beads, has been characterized by a variety of techniques, namely, scanning electron microscopy and Fourier transform infrared spectroscopy. A plausible reaction mechanism for the hydrogen-bond assisted ring-opening of aziridine to five-membered 5-aryl-2-oxazolidinones is also proposed.

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