Fe-catalyzed Synthesis Of Thioglysides

As one of the essential elements for organisms,Iron and its compounds featuring the biocompatibility are environmentally benign.Iron is of great value in organic synthesis because it acts as the efficient catalyst.The iron halides as common Lewis acids,prone to coordinate stably with such atoms as oxygen,phosphorus and nitrogen,are able to catalyze various types of reactions.Their use in the combination with other metal else showed a synergistic effect on the catalytic reaction,providing the shorter reaction time and the higher yields.Especially,iron can catalyze the formation of C-S bonds to afford thioethers.The synthesis and application of carbohydrate derivatives remain the subject of great interest because of the remarkable biological relevance of carbohydrate motifs.Among them thioglycosides constitute a valuable class of functional compounds,in which a sulfur atom has replaced the glycosidic oxygen atom.These glycomimetics exhibit apparent advantages over their parent molecules because they can enhance the metabolic stability and might lead to the rational design of new generations of therapeutic agents.Additionally,a large number of naturally occurring antibiotics and antitumors possess thioglycoses as crucial structural moieties.As thioglycosides are usually stable under many protecting group transformations,multifunctional derivatives are produced relatively easily.Also,they serve as practical precursors for the preparation of glycosyl fluorides,halides,and sulfoxides,which have utilities as glycosyl donors in the O-glycoside synthesis.In particular,thioglycosides,featuring the tunable reactivity dependent on different protecting groups,have been established to be attractive building blocks for the one-pot sequential assembly of complex oligosaccharides.Thus,synthesis of these organsulfur compounds with high efficiency is greatly desirable.In this paper,the catalytic reactions using iron are firstly summarized.Then based on the recently iron-catalyzed the formation of C-S bonds,we performed the study about Fe-mediated thioglycoside synthesis.And the effects of different iron catalysts on the yields and stereoselectivity of thioglycosides were also discussed.In the presence of FeCl3 in combination with [BMIM] · [NTf2],the reactions of aldosyl acetates with arylthiols smoothly produced the desired thioglycosides in the handsome yields.Mild condition,broad scopes of substrates,good stereoselectivity,and compatibility of common protective groups featured the thioglycosylation protocol.