Solvent-free synthesis of glycosyl chlorides based on the triphenyl phosphine/hexachloroacetone system

Traboni, Serena; Liccardo, Federica; Bedini, Emiliano; Giordano, Maddalena; Iadonisi, Alfonso

doi:10.1016/j.tetlet.2017.03.068

Cited by 16 publications

(9 citation statements)

References 40 publications

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“…Another solvent-free, noncatalytic approach was developed to carry out the anomeric chlorination of hemiacetal sugars to yield useful glycosyl donors for the synthesis of glycosides. The method relies on the use of a moderate excess of hexachloroacetone and triphenyphosphine at 70 • C, a procedure that appears compatible with both acid-and base-labile protecting groups [65]. As will be shown below, this step can be incorporated into one-pot sequences leading to glycoside synthesis.…”

Section: Solvent-free Halogenation Of Saccharide Substratesmentioning

confidence: 99%

Solvent-Free Approaches in Carbohydrate Synthetic Chemistry: Role of Catalysis in Reactivity and Selectivity

et al. 2020

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Owing to their abundance in biomass and availability at a low cost, carbohydrates are very useful precursors for products of interest in a broad range of scientific applications. For example, they can be either converted into basic chemicals or used as chiral precursors for the synthesis of potentially bioactive molecules, even including nonsaccharide targets; in addition, there is also a broad interest toward the potential of synthetic sugar-containing structures in the field of functional materials. Synthetic elaboration of carbohydrates, in both the selective modification of functional groups and the assembly of oligomeric structures, is not trivial and often entails experimentally demanding approaches practiced by specialized groups. Over the last years, a large number of solvent-free synthetic methods have appeared in the literature, often being endowed with several advantages such as greenness, experimental simplicity, and a larger scope than analogous reactions in solution. Most of these methods are catalytically promoted, and the catalyst often plays a key role in the selectivity associated with the process. This review aims to describe the significant recent contributions in the solvent-free synthetic chemistry of carbohydrates, devoting a special critical focus on both the mechanistic role of the catalysts employed and the differences evidenced so far with corresponding methods in solution.

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Section: Solvent-free Halogenation Of Saccharide Substratesmentioning

confidence: 99%

Solvent-Free Approaches in Carbohydrate Synthetic Chemistry: Role of Catalysis in Reactivity and Selectivity

et al. 2020

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“…Glycosyl halides (chlorides, bromides, iodides, and fluorides) are important glycosyl donors that are used for the synthesis of O ‐, C ‐, and N ‐glycosides Excellent progress has been made in the synthesis of α‐glycosyl chlorides by several methods, including the use of metal halides (SnCl 4 and TiCl 4 ), PPh 3 /CCl 4 , DMF/trichlorotriazine, oxalyl chloride, triphosgene, PPh 3 /hexachloroacetone, and others . Ideally, the chlorinating agent should have a wide substrate scope, show tolerance to labile sugar protecting groups, be convenient to use so that harsh chlorination conditions are avoided, require short reaction times, and allow for easy separation of the products.…”

Section: Introductionmentioning

confidence: 99%

“…In this way we could avoid multistep reactions and tedious purifications. This became even more imperative since some α‐glycosyl chlorides decompose during purification by silica gel column chromatography or during storage , . For this purpose, we reinvestigated the synthesis of α‐glycosyl chlorides, aiming to develop a simple synthetic approach that would tolerate typical sugar protecting groups and at the same time enable direct one‐pot glycosylation.…”

Section: Introductionmentioning

confidence: 99%

Efficient Synthesis of α‐Glycosyl Chlorides Using 2‐Chloro‐1,3‐dimethylimidazolinium Chloride: A Convenient Protocol for Quick One‐Pot Glycosylation

2018

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A mild and convenient method for the synthesis of α‐glycosyl chlorides in high 80–96 % yields within 15–30 min using 2‐chloro‐1,3‐dimethylimidazolinium chloride (DMC) is disclosed. The method has a wide substrate scope and is compatible with labile OH protecting groups, including benzyl, acetyl, benzoyl, isopropylidene, benzylidene, TBDMS (tert‐butyldimethylsilyl), and TBDPS (tert‐butyldiphenylsilyl) groups. The excellent α selectivity obtained in this reaction is attributed to in‐situ isomerization of β‐glycosyl chlorides to the more stable α‐glycosyl chlorides, as demonstrated by 1H NMR spectroscopic studies. Disarmed sugars with OBz or OAc groups at C‐2 were chlorinated at a faster rate but ismomerized (β→α) at a slower rate than armed sugars with an OBn group at C‐2. More importantly, the method enables highly desirable one‐pot glycosylation reactions to take place, thus allowing efficient syntheses of disaccharides and simple O‐glycosylated sugars in high overall yields without the need for separation or purification of the α‐glycosyl chloride donors. This method will be especially useful for direct glycosylation reactions using glycosyl chloride donors that are unstable upon separation and purification.

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“…We reported a convenient protocol for regioselective benzylation of primary hydroxyl groups on carbohydrates, the first catalytic tin–mediated approach to regioselective alkylation of secondary hydroxyls, and three solvent–free acetalation protocols . More recently, we demonstrated the applicability of solvent–free conditions in the assembly of saccharide building blocks through regioselective silylation or tritylation and for the convenient preparation of glycosyl chlorides using PPh 3 /hexachloroacetone combined system . Reactions performed in the absence of solvent can be considered both economically and environmentally advantageous, allowing reduction of polluting waste and costs, shorter reaction times, simplification of the experimental procedure and work–up, especially when tedious evaporation of high boiling and toxic solvents would be required.…”

Section: Introductionmentioning

confidence: 99%

Solvent‐Free Conversion of Alcohols to Alkyl Iodides and One‐Pot Elaborations Thereof

2018

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Combination of iodine and triphenylphosphine in the presence of a slight stoichiometric excess of 2,6‐lutidine provided effective iodination of alcohols under solvent–free conditions. Several substrates with different polarity, not necessarily soluble in the reaction system, were iodinated in short times without the need for microwave irradiation, ultrasonication or ionic liquids. The scope of this method with complex molecules was especially demonstrated in the fast and selective iodination of primary hydroxyl groups on both protected and unprotected carbohydrates, proving compatible with a variety of functional groups. In addition, a large number of one – pot elaborations of alkyl iodides thus obtained was successfully performed through the application of unprecedented fully solvent – free sequences. In particular, direct installation of either nitrogen or sulfur functionalities and generation of useful saccharide building – blocks were achieved in remarkably short times avoiding the use of polar high boiling solvents.

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Solvent-free synthesis of glycosyl chlorides based on the triphenyl phosphine/hexachloroacetone system

Cited by 16 publications

References 40 publications

Solvent-Free Approaches in Carbohydrate Synthetic Chemistry: Role of Catalysis in Reactivity and Selectivity

Solvent-Free Approaches in Carbohydrate Synthetic Chemistry: Role of Catalysis in Reactivity and Selectivity

Efficient Synthesis of α‐Glycosyl Chlorides Using 2‐Chloro‐1,3‐dimethylimidazolinium Chloride: A Convenient Protocol for Quick One‐Pot Glycosylation

Solvent‐Free Conversion of Alcohols to Alkyl Iodides and One‐Pot Elaborations Thereof

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