No abstract

Cu-Fe spinels promoted the Ferrier rearrangement of 2-nitroglycals with several O-nucleophiles. 2,3-Unsaturated carbohydrate derivatives were prepared by the reaction of 3,4,6-tri-Oacetyl- 2-nitroglucal and alcohols in the presence of 5 % of CuFe2O4. After separation of the catalyst with an external magnet, the reaction products were obtained in good yields and high stereo and regioselectivity. Also, S- and heterocyclic C-3 substituted 2-nitro-endo-glycals could be prepared by this method.

Background: The ionic liquid triethylammonium acetate (TEAA) was found to be an efficient solvent in the acetylation of alcohols, amines, oximes and thiols to their corresponding acetyl compounds using only a 10% excess of acetic anhydride under mild conditions. Moreover TEAA is not only an inexpensive and recyclable solvent but also an anomeric selective catalyst in the per-Oacetylation of sugar moieties.Methods: Simple and effective organic synthesis protocols were provided for the selective acetylation of several substrates. The products were fully characterized by 1 H and 13 C NMR spectroscopy and the anomeric ratios were obtained from the 1 H spectra.Results: Structurally diverse alcohols, phenols, thiols, amines, carbohydrates and oximes underwent acylation under mild conditions by this procedure to provide the corresponding acetates in excellent yields. TEAA ionic liquid is unique in its capability to act as both, solvent and high selective catalyst. As expected, the reaction proceeds with high b anomeric selectivity for sugars derivatives. Moreover, the ionic liquid was regenerated, recycled and reused for three times without apparent loss of reactivity and selectivity in all cases. Conclusions:The present procedure provides a powerful and versatile acylation method for alcohols, phenols, thiols, amines, oximes and carbohydrates. This protocol is endowed with several unique merits: selectivity, cost-efficiency, atom-economy and mild reaction conditions tolerable to acid sensitive functionalities. With these features, this method may be considered as a better alternative for the acetylation of a wide range of substrates.

A synthetic route for the production of chiral derivatives of benzimidazole is presented. Different commercially available amines were evaluated as organocatalysts for the stereoselective aldol addition of N-1 benzimidazolyl acetaldehyde, previously prepared by N-alkylation of benzimidazole, with cyclic ketones. When cyclohexanone was used, L-prolinamide proved to be the most efficient catalyst, giving (S)-2-((R)-2-(1H-benzo[d]imidazol-1-yl)-1-hydroxyethyl) cyclohexanone 92% yield, 90% ee and 92:8 dr (anti:syn).

Several β-N-glycosides were obtained upon a simple and efficient two-step methodology. First, α-1,2-anhydrosugars were prepared diastereoselectively by the oxidation of 3,4,6-tri-O-benzyl-D-glucal under biphasic conditions (CH 2 Cl 2 /water) using dimetyldioxirane (DMDO) generated in situ from oxone/ acetone mixture and amphiphilic imidazolium ionic liquid (DodMImBF 4 ) as phase transfer catalyst. Immediately, β-Nglycosides were synthesized in good yields by aminolysis of these α-1,2-anhydrosugars using CH 3 CN as solvent. The overall process allows stereoselective generation of biologically relevant carbohydrate derivatives. ChemistrySelectCommunications