Acetyl chloride-silver nitrate-acetonitrile: a reagent system for the synthesis of 2-nitroglycals and 2-nitro-1-acetamido sugars from glycals

A new reagent system comprising acetyl chloride, silver nitrate, and acetonitrile has been developed for the synthesis of 2-nitroglycals from the corresponding glycals. Under certain conditions, the formation of 2-nitro-1-acetamido sugars has also been observed. In addition, a few other non-carbohydrate-derived olefins also gave the corrresponding conjugated nitroolefins.     

LaCl3·7H2O/NaI/benzyl alcohol: a novel reagent system for regioselective hydration of glycals: application in the synthesis of 1,6-dideoxynojirimycin

Glycals can be readily hydrated using the LaCl₃·7H₂O/NaI/PhCH₂OH reagent system. In one case, having an exo methylene group, such hydration gives an intermediate which is readily converted into 1,6-dideoxynojirimycin, a potential enzyme inhibitor.     

InCl3/IBX: a novel reagent system for the conversion of glycals into α,β-unsaturated δ-lactones

The combination of indium trichloride with iodoxybenzoic acid (IBX) has been utilized for the first time as a novel reagent system for the one-pot synthesis of 2,3-dideoxy-d-hex-2-enono-1,5-lactones from glycals. The reaction proceeds smoothly in aqueous media and the products are obtained in good yields. This method is suitable for the oxidation of glycals bearing olefin functionality.     

A facile method for the synthesis of novel imidoyl iminosulfuranes from imidoyl azides

A novel and environmentally friendly method for the one-pot preparation of new imidoyl iminosulfuranes in high yield under microwave (MW) and solvent-free conditions from the corresponding imidoyl azides is presented. This efficient synthetic approach benefits from non-toxic and non-explosive precursors for the synthesis of imidoyl iminosulfuranes.     

Rapid and facile synthesis of acyl azides from acyl halides using a polymer-supported azide ion under heterogeneous conditions

In this article a rapid and facile method for synthesis of acyl azide is described. The cross-linked poly(N-methyl-4-vinylpyridinium) azide ion, [P₄-VP]N₃ is prepared and used as an efficient polymeric reagent for synthesis of acyl azides from acyl halides at room temperature under heterogeneous conditions. Various benzoyl halides, with electron-withdrawing groups as well as electron-donating groups, were transformed into the corresponding benzoyl azides in high to excellent yields in short reaction times. The acyl azide products were characterized by FT-IR, and some of them were also characterized by ¹H-and/or ¹³C-NMR spectroscopy, and physical properties were compared to literature values of known compounds. The spent polymeric reagents can be regenerated and reused for several times without losing their activity. Relative to the reported methods, the present method has the advantages of operational simplicity, mild reaction conditions, fast reaction rates, simple reaction work-up and lower hazardous and potentially explosive nature. Also the present method is the first procedure for the synthesis of acyl azides from acyl halides by using a polymer-supported azide ion under heterogeneous conditions.     

Oxidation of azides by the HOF.CH3CN: a novel synthesis of nitro compounds

The HOF.CH3CN complex, readily prepared by passing F2 through aqueous acetonitrile, is an exceptionally efficient oxygen transfer agent. It is unique in its capacity to oxidize various azides into the corresponding nitro derivatives. This method requires short reactions times and room temperature or below, and the desired nitro compounds were usually isolated in very good yields. The respective nitroso derivatives are believed to be the intermediates in this reaction. Functional groups such as aromatic rings, ketones, nitriles, halides, alcohols, and esters are tolerated. Sulfides react with HOF.CH3CN usually at the same rate as azides. Amines and olefins, however, react faster, so they have to be protected first. Nitro derivatives with various oxygen isotopes can be made using the labeled H18OF.CH3CN. In the case of chiral azides the stereochemistry around the nitrogen-bonded carbons is retained.     

The Vilsmeier reagent: a useful and versatile reagent for the synthesis of 2-azetidinones

(Chloromethylene)dimethylammonium chloride (Vilsmeier reagent), prepared easily from N,N-dimethylformamide and oxalyl chloride or thionyl chloride, works as a versatile acid activator reagent for the direct [2+2] ketene-imine cycloaddition of substituted acetic acid and imines in one-pot synthesis under mild conditions. Monocyclic, spirocyclic and 3-electron-withdrawing group β-lactams were synthesized by this method and optimization of conditions were performed.     

Iodine/MeOH as a novel and versatile reagent system for the synthesis of α-ketothiocyanates

Ketones possessing α-hydrogens undergo smooth thiocyanation with ammonium thiocyanate in the presence of molecular iodine in refluxing methanol to produce the corresponding α-ketothiocyanates in excellent yields with high selectivity. The use of iodine makes this procedure simple, convenient and cost effective.     

Flow synthesis of organic azides and the multistep synthesis of imines and amines using a new monolithic triphenylphosphine reagent

Here we describe general flow processes for the synthesis of alkyl and aryl azides, and the development of a new monolithic triphenylphosphine reagent, which provides a convenient format for the use of this versatile reagent in flow. The utility of these new tools was demonstrated by their application to a flow Staudinger aza-Wittig reaction sequence. Finally, a multistep aza-Wittig, reduction and purification flow process was designed, allowing access to amine products in an automated fashion.     

Addition of aryl cuprates to azides: a novel approach for the synthesis of unsymmetrical diaryl amines

Aryl and benzyl azides react smoothly with aryl cuprates, generated in situ from aryl magnesium bromide and CuCN in THF to furnish a variety of unsymmetrical diaryl amines in good yields. This is the first report on the synthesis of diarylamines from aryl azides and aryl bromides via an organometallic approach.     

Reaction of allenyl esters with sodium azide: an efficient synthesis of e-vinyl azides and polysubstituted pyrroles

The nucleophilic addition of sodium azide to 1,2-allenyl esters can generate vinyl azides in excellent yields with excellent regio- and stereoselectivities. Moreover, pyrroles are synthesized using 1-allyllic 1,2-allenyl esters as substrates in t-BuOH at 65 degrees C. The sequential reaction for pyrroles is developed on the basis of a novel domino process involving nucleophilic addition, cycloaddition, denitrogenation, and aromatization.     

Design and synthesis of a highly efficient labelling reagent for incorporation of tetrafluorinated aromatic azide into proteins

Chemical labelling can significantly extend the structures and functions of proteins for advanced applications. Herein, a highly efficient bench-stable reagent diazo-azide was designed and synthesized for the incorporation of tetrafluorinated aromatic azides into proteins via the diazonium coupling. The diazo-azide-labelled proteins could be further functionalized via the nonhydrolysis Staudinger reaction to achieve fluorescence labelling, PEGylation and biotinylation. The whole protein labelling processes were catalysis-free and could be finished within several hours under the mild conditions. To this end, we have prepared thickened viral nanoparticles with controllable diameters.     

Selectfluor™: a novel and efficient reagent for the synthesis of β-hydroxy thiocyanates

A variety of epoxides undergo rapid ring opening with ammonium thiocyanate in the presence of 10 mol % Selectfluor™ in acetonitrile at room temperature to afford the corresponding β-hydroxy thiocyanates in excellent yields with high regioselectivity.     

A convenient and efficient method for the synthesis of 2-hydroxy glycals

A convenient and efficient method for preparing 2-hydroxy glycals was developed from thioglycosides by using 1,4-dioxane-bromine complex/DMAP as an efficient promoter with good yield (61-85%). In this synthetic method, a wide range of sugar thioglycosides could be used as substrates.     

A versatile strategy for the synthesis of N-linked glycoamino acids from glycals

A versatile route for the synthesis of N-linked glycoamino acids from readily available glycals is reported. A variety of glycals possessing different carbohydrate templates (mono-, di- and trisaccharide glycals) were shown to undergo a novel iodine catalyzed stereoselective diamination reaction with chloramine-T. Taking advantage of the difference in the reactivity between the anomeric and C2 sulfonamido groups of these diamines 7, 13, 15, 17 and 19, they could be protected differentially at the C2 and anomeric nitrogen atoms. Thus, chemoselective acetylation of these diamines installed the C2 acetamido group, an essential functionality that plays a crucial role in inducing a beta-turn in N-linked glycoproteins. Subsequent protection of the anomeric nitrogens of 20a,b,e as their Alloc (allyloxycarbonyl) derivatives followed by SmI(2) mediated facile didetosylation afforded 24a-c. Deprotection of the Alloc group of 24a and 24c and coupling of the liberated free amine with a variety of protected amino acids provided N-linked glycoamino acids 25 and 27 in high yields. An illustrative synthesis of an N-linked glycopeptide 29 is also reported.