- In a 1 -litre three-necked round-bottomed flask fitted with an efficient stirrer and a reflux condenser, place 170g (0.5 mol) of 1,2:5,6-di-o-cyclohexylidene-𝛼-D-glucofuranose, 8.1 g (0.025 mol) of tetrabutylammonium hydrogen sulphate, 400ml of (E)-l,2-dichloroethylene, 76 g (0.6 mol) of benzyl chloride and a solution of 120 g (3 mol) of sodium hydroxide in 120 g of water.
- Stir the reaction mixture vigorously and heat under reflux.
- Thin-layer chromatography analysis (silica gel plates and ethyl acetate as developing solvent) shows the reaction to be complete within 2 hours.
- Cool the mixture and pour into 1 litre of water, separate the organic layer, wash, dry and evaporate.
- Distil the viscous yellow residue in a molecular still (Section 2.28) using a vapour diffusion pump.
- There is obtained a small forerun followed by the main fraction of 3-o-benzyl-l,2:5,6-di-o-cyclohexylidene-𝛼-D-glucofuranose, which distils at a temperature of 210-220 °C/ 10 mmHg. The yield is 172g (79%), [𝛼]ᴅ²⁰ -13.0° (c5 in CHCl₃).
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