Selective Conversion of Malononitrile and Unprotected Carbohydrates to Bicyclic Polyhydroxyalkyl Dihydrofurans Using Magnesium Oxide as a Recyclable Catalyst

Abstract

Using renewable feedstocks to access highly functionalized molecules in a concise manner is a promising approach to sustainable syntheses. Previous studies used malononitrile to convert simple sugars to polyhydroxylalkyl aminofurans in the presence of various catalysts. Herein, a chemodivergent method is disclosed for the reaction of the same unprotected sugars with malononitrile to instead form bicyclic 2,3-dihydrofuran products in yields up to 85% with good regioselectivities. Kinetic, NMR, and computational studies support a proposed mechanism for the formation of dihydrofuran products. By employing a mild set of reaction conditions (aqueous solvent, at room temperature, in under 4 h) and a recyclable heterogeneous MgO catalyst, this method serves as a powerful tool for carbohydrate upcycling that offers useful and interesting nonaromatic products.