Phenyliodine Bis(trifluoroacetate) (PIFA) as an Excellent Promoter of 2-Deoxy-2-phthalimido-1-thioglycosides in the Presence of Triflic Acid in Glycosylation Reactions

Hypervalent Iodine Compounds in Carbohydrate Chemistry: Glycosylation, Functionalization and Oxidation

This mini review article provides an overview on the use of hypervalent iodine compounds (HICs) in carbohydrate synthesis, focusing on their chemistry and recent applications. HICs are similar to transition metals in their reactivity but have the added benefit of being environmentally benign, and are therefore commonly used as selective oxidants and eco-friendly reagents in organic synthesis. Herein, we summarize various synthetic uses of hypervalent iodine reagents in reactions such as glycosylation, oxidations, functionalization, and C-C bond-forming reactions. The goal of this review is to illustrate the advantages and versatility of using HICs as an environmentally sustainable alternative to heavy metals in carbohydrate chemistry.

Phenyliodine bis(trifluoroacetate) as a sustainable reagent: exploring its significance in organic synthesis

Iodine-containing molecules, especially hypervalent iodine compounds, have gained significant attention in organic synthesis. They are valuable and sustainable reagents, leading to a remarkable surge in their use for chemical transformations. One such hypervalent iodine compound, phenyliodine bis(trifluoroacetate)/bis(trifluoroacetoxy)iodobenzene, commonly referred to as PIFA, has emerged as a prominent candidate due to its attributes of facile manipulation, moderate reactivity, low toxicity, and ready availability. PIFA presents an auspicious prospect as a substitute for costly organometallic catalysts and environmentally hazardous oxidants containing heavy metals. PIFA exhibits remarkable catalytic activity, facilitating an array of consequential organic reactions, including sulfenylation, alkylarylation, oxidative coupling, cascade reactions, amination, amidation, ring-rearrangement, carboxylation, and numerous others. Over the past decade, the application of PIFA in synthetic chemistry has witnessed substantial growth, necessitating an updated exploration of this field. In this discourse, we present a concise overview of PIFA's applications as a 'green' reagent in the domain of synthetic organic chemistry. A primary objective of this article is to bring to the forefront the scientific community's awareness of the merits associated with adopting PIFA as an environmentally conscientious alternative to heavy metals.

Iodosylbenzene-Promoted Glycosylation with Selenoglycosides: Application in One-Pot Glycosylation

A novel method for the glycosylation of selenoglycosides activated by iodosylbenzene was developed. The glycosylation reaction conditions were mild, fast, and efficient, with a high tolerance to diverse protecting groups and a wide substrate scope, which is advantageous for synthesizing complex glycosides. In addition, selenoglycosides were shown to be orthogonal to thioglycosides under the promotion of iodosylbenzene. Notably, a high yield of the poorly reactive glucuronidation reaction product was obtained by acetyl-protected selenoglycoside. Finally, the orthogonal one-pot synthesis of β-(1→6) oligoglucans demonstrated the usefulness of this method in oligosaccharide synthesis.

Metal-Free Oxidative Cross-Coupling Reaction of Heteroaromatic and Related Compounds

The biary unit having heteroatom as important scaffolds widely exist in a large number of biologically active compounds and functional organic molecules. Since the cross-coupling is a useful synthetic method for constructing biaryl and heterobiaryl structures, the development of novel cross-coupling methods has been studied intensively. The oxidative biaryl coupling reaction of aromatic compounds having heteroatoms is an attractive method since they do not require the prefunctionalization of arenes. This report describes recent advances in hypervalent iodine(III) induced metal-free synthesis of biaryls having heteroatoms.

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

To synthesize nucleoside and oligosaccharide derivatives, we often use a glycosylation reaction to form a glycoside bond. Coupling reactions between a nucleobase and a sugar donor in the former case, and the reaction between an acceptor and a sugar donor of in the latter are carried out in the presence of an appropriate activator. As an activator of the glycosylation, a combination of a Lewis acid catalyst and a hypervalent iodine was developed for synthesizing 4'-thionucleosides, which could be applied for the synthesis of 4'-selenonucleosides as well. The extension of hypervalent iodine-mediated glycosylation allowed us to couple a nucleobase with cyclic allylsilanes and glycal derivatives to yield carbocyclic nucleosides and 2',3'-unsaturated nucleosides, respectively. In addition, the combination of hypervalent iodine and Lewis acid could be used for the glycosylation of glycals and thioglycosides to produce disaccharides. In this paper, we review the use of hypervalent iodine-mediated glycosylation reactions for the synthesis of nucleosides and oligosaccharide derivatives.

Chemical O-Glycosylations: An Overview

The development of glycobiology relies on the sources of particular oligosaccharides in their purest forms. As the isolation of the oligosaccharide structures from natural sources is not a reliable option for providing samples with homogeneity, chemical means become pertinent. The growing demand for diverse oligosaccharide structures has prompted the advancement of chemical strategies to stitch sugar molecules with precise stereo- and regioselectivity through the formation of glycosidic bonds. This Review will focus on the key developments towards chemical O-glycosylations in the current century. Synthesis of novel glycosyl donors and acceptors and their unique activation for successful glycosylation are discussed. This Review concludes with a summary of recent developments and comments on future prospects.

Efficient O-Functionalization of Carbohydrates with Electrophilic Reagents

Novel methodology for O-functionalization of carbohydrate derivatives has been established using bench-stable and easily prepared iodonium(III) reagents. Both electron-withdrawing and electron-donating aryl groups were introduced under ambient conditions and without precautions to exclude air or moisture. Furthermore, the approach was extended both to full arylation of cyclodextrin, and to trifluoroethylation of carbohydrate derivatives. This is the first general approach to introduce traditionally non-electrophilic groups into any of the OH groups around the sugar backbone. The methodology will be useful both in synthetic organic chemistry and biochemistry, as important functional groups can be incorporated under simple and robust reaction conditions in a fast and efficient manner.