RESUMO
Multistep reactions are often required for the transformation of alcohols to α-chloroacetals via the unstable intermediates aldehydes or α-halo aldehydes. Herein, we report a simplified procedure for practical synthesis of α-chloroacetals using 2,2,6,6-tetramethylpiperidine-1-oxyl as a catalyst and trichloroisocyanuric acid both as an oxidant and a chlorination reagent. The reaction is one-pot, solvent-free and high-yielding. In addition, the α-chloroacetals have been transformed to enol ethers through the elimination reaction in the presence of sodium.
RESUMO
A Cu(ii)-mediated synthesis of N,N'-diacylhydrazines and 1,3,4-oxadiazoles from aldehyde hydrazones has been developed. This is the first time that the synthesis of N,N'-diacylhydrazines and 1,3,4-oxadiazoles using N,N-dimethylamides as the acylation reagent and O2 in air as the oxidation reagent is reported. These reactions offered several advantages including simple workups, ligand-free inexpensive metal salts as mediators, high yields, and wide scope of substrates.
RESUMO
A new method of synthesizing ß-glycosyl esters stereospecifically has been developed by treating O-benzyl-protected glycosyl chlorides with Cs2CO3, tetrabutylammomium bromide (TBAB), a carboxylic acid, water, and granular polytetrafluoroethylene (PTFE) at 80 °C under mechanical agitation. D-Glucosyl, D-xylosyl, and D-galactosyl chlorides and 20 carboxylic acids were used to demonstrate the scope of the reaction. Control experiments showed that the water and granular PTFE had indispensable roles. Water-soluble TBAB has been found to be as efficient as N-methyl-N,N,N-trioctyloctan-1-ammonium chloride (Aliquat 336) in the reactions. After scaling up to 5-12 g, all of the products were obtained quantitatively via simple filtration and no organic solvents or chromatography was needed for the entire process.