Synthesis and Applications of Carbohydrate-Based Organocatalysts

Abstract

Organocatalysis is a very useful tool for the asymmetric synthesis of biologically or pharmacologically active compounds because it avoids the use of noxious metals, which are difficult to eliminate from the target products. Moreover, in many cases, the organocatalysed reactions can be performed in benign solvents and do not require anhydrous conditions. It is well-known that most of the above-mentioned reactions are promoted by a simple aminoacid, l-proline, or, to a lesser extent, by the more complex cinchona alkaloids. However, during the past three decades, other enantiopure natural compounds, the carbohydrates, have been employed as organocatalysts. In the present exhaustive review, the detailed preparation of all the sugar-based organocatalysts as well as their catalytic properties are described.

Growing Impact of Carbohydrate‐Based Organocatalysts

“…A number of carbohydrate-derived organocatalysts have been developed in past two decades which have catalyzed a wide spectrum of organic reactions including epoxidation, Michael addition, aldol reaction, aza-Henry reaction, Mannich reaction, Biginelli reaction with remarkable advantages over conventional catalysts, such as, very low catalyst loading, aqueous medium catalysis, solvent-free catalysis, green catalysis for drug synthesis etc. [12,13] Scheme 3. First examples of sugar-derived ligands to achieve asymmetry.…”

“…[9] Since the interest of chemistry community directed towards the organocatalysis, biomolecules have been the first choice to develop this type of catalysts to ensure a low-cost catalysis in general and green catalysis for drug synthesis. Among some common biomolecules, proline, [10] cinchona alkaloids, [11] and carbohydrates [12,13] are the most favored or privileged molecules which have been explored as organocatalysts in their original form, as well as, in derivative forms with some structural modifications. Among these preferred molecules, carbohydrates because of some unique traits have emerged as a very promising scaffold during last two decades for the development of efficient organocatalysts.…”

Triazole-Appended Glycohybrid/CuI-Catalyzed C–C Cross-Coupling of Aryl/Heteroaryl Halides with Alkynyl Sugars

“…Ma's group reported a series of potential ligands that efficiently support Cu-catalysis. 32−37 In addition to existing ligands, the application of sugar-based molecules as ligands and catalysts is ever expanding; 38,39 however, it is yet limited in these coupling reactions. The natural abundance, chirality, molecular architecture, and multiple binding sites associated with the carbohydrate molecules aid them as a suitable scaffold for the synthesis of metal−ligand systems and organocatalysts.…”

“…Numerous reports describe both conventional and new ligands in transition metal catalysis. Ma's group reported a series of potential ligands that efficiently support Cu-catalysis. − In addition to existing ligands, the application of sugar-based molecules as ligands and catalysts is ever expanding; , however, it is yet limited in these coupling reactions. The natural abundance, chirality, molecular architecture, and multiple binding sites associated with the carbohydrate molecules aid them as a suitable scaffold for the synthesis of metal–ligand systems and organocatalysts. ,, The sugar-derived ligands, such as glycosylated 1,2,3-triazoles or triazole-appended glycohybrids, have an increasing impact on metal-catalyzed coupling reactions. − Interestingly, carbohydrate-containing 1,2,3-triazoles obtained via a regioselective Cu-catalyzed azide–alkyne cycloaddition (CuAAC) modular tool have displayed enormous applications in various emerging fields ranging from medicinal chemistry to catalysis. − Herein, we explored the regioselective CuAAC protocol and developed novel 1,2,3-triazole-appended glycohybrids and screened them as ligands with monotriazolyl and bis-triazolyl rings for the Cu-catalyzed Sonogashira reaction in order to explore their efficient metal-coordinating properties.…”

Shaping MOF oxime oxidation catalysts as three-dimensional porous aerogels through structure-directing growth inside chitosan microspheres

“…The use of polysaccharides as catalysts or catalytic supports has emerged in the last decade and is significantly promoting sustainable catalysis. [33][34][35][36][37] Harnessing indeed the structure-directing ability of polysaccharides for shaping MOFs could promote their sustainability, with respect to other routes involving synthetic, yet non-degradable polymeric materials. 25,[38][39][40] Hitherto, the involvement of natural carbohydrates relied mostly on their use as organic binders to shape an already existing MOF, with absolutely no control over the size or the texture of the corresponding material.…”