Three Solvent‐Free Catalytic Approaches to the Acetal Functionalization of Carbohydrates and Their Applicability to One‐Pot Generation of Orthogonally Protected Building Blocks

Abstract

Abstract Three alternative protocols were developed to carry out the selective installation of acetal groups on carbohydrates and polyols under mildly acidic, solvent‐free conditions. One protocol is based on a diol/aldehyde condensation at room temperature, with an acetolysis process serving for the activation of the carbonyl component. A second approach is based on an orthoester‐mediated activation of the carbonyl component at high temperature. The third protocol is instead entailing a transacetalation mechanism. Combination of these methods allows a wide set of acetal‐protected building blocks to be accessed in short times under very simple experimental conditions working under air. The scope of the latter two approaches was also extended to unusual one‐pot synthetic sequences leading to concomitant Fischer glycosidation/acetal protection of reducing sugars. magnified image