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The primary alcohol function of essentially unprotected carbohydrates (methyl‐α‐D‐mannopyranoside, methyl‐α‐D‐glucopyranoside and methyl‐α‐D‐galactopyranoside) was selectively converted into the corresponding aldehyde in the form of acetals by using TEMPO+ BF4– (2,2,6,6‐tetramethylpiperidine‐1‐oxoammonium tetrafluoroborate) in organic medium with 2,6‐lutidine as the base. Indeed, organic anhydrous conditions prevent over oxidation of the alcohol group to the carboxylate form. The resulting compounds, methyl‐α‐D‐glucohexodialdo‐1,5‐pyranoside and methyl‐α‐D‐manohexodialdo‐1,5‐pyranoside were characterized by NMR and mass spectrometry. Additionally, the results obtained in a TEMPO electrochemically mediated system were compared with those of the pure TEMPO+ BF4– system, but lower yields were attained under the electrochemical conditions as a result of a very slow reaction rate. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The microwave-assisted intramolecular [3 + 2] cycloaddition reaction of azomethine ylides to activated and nonactivated alkenes and alkynes is described. The procedure allows the synthesis of pyrrolidines and pyrrole products in good to excellent overall yields in short reaction times. It appears from parallel comparative studies that the microwave procedure favors the reaction times and overall purity of the crude reaction mixture. The reactions can also be performed in the absence of solvent. [reaction: see text]

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