Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

1.73 g of a mixture of 80% of EDT-methanol and 20% of hydroxy-PDT (corresponding to 8.08 mmol of EDT-methanol), 1.64 g of N,N′-dicyclohexyl-carbodiimide and 0.13 g of 4-(dimethylamino)pyridine are dissolved in 100 ml of CH2Cl2 and cooled to about 0° C. in an ice bath. 2.00 g of [(4′-cyano-1,1′-biphenyl-4-yl)oxy]acetic acid are added thereto a little at a time over a period of 1 hour while stirring and cooling in ice. The reaction is then continued at 23° C. for 42.5 hours. The N,N′-dicyclohexylurea formed is subsequently filtered off. The filtrate is washed in succession with 2×200 ml of 1 M HCl, 2×200 ml of saturated NaHCO3 solution and 2×200 ml of saturated NaCl solution. The organic phase is dried over MgSO4 and, after the magnesium sulphate has been filtered off, freed of solvent on a rotary evaporator. This gives 3.71 g of crude product which is purified by column chromatography using n-hexane/ethyl acetate 3:2. 0.39 g of the pure ester of EDT-methanol (I-a2) is obtained as colourless crystals.

Herkunft & Nachweise