Page 75 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant
P. 75

60             hydrolysis, oxidation and reduction

               . 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU, 98 %) three drops, 90 mg,
                  32 mmol
               . Ethyl acetate, petroleum ether
               . Brine
               . Magnesium sulfate

               . Two 10 mL round-bottomed flasks with magnetic stirrer bars
               . Magnetic stirrer
               . Bu Èchner funnel (5 cm)
               . Bu Èchner flask
               . Filter paper
               . Separating funnel, 250 mL
               . Rotary evaporator


               Procedure
               1. In a 10 mL round-bottomed flask equipped with a magnetic stirrer bar
                  were placed tetrahydrofuran (0.8 mL) and immobilized poly-d-leucine
                  (100 mg). (E)-Benzylideneacetophenone (50 mg), 1,8-diazabicyclo[5.4.0]
                  undec-7-ene (90 mg), and urea±hydrogen peroxide (27 mg) were added to
                  the mixture. The thick white reaction mixture was stirred vigorously for 30
                  minutes.
               2. The reaction was monitored by TLC (eluent: petroleum ether±ethyl acetate,
                  4:1). Visualized by p-anisaldehyde dip, the chalcone stained brown, R f 0.42
                  and the epoxide stained blue, R f 0.36.
               3. After completion, the mixture was poured into ethyl acetate and the catalyst
                  was removed by filtration using two filter papers in a Bu Èchner funnel. The
                  poly-d-leucine residue was washed with ethyl acetate (2   10 mL), with
                  water (2   10 mL) and with brine (10 mL).
               4. The mixture was transferred into a separating funnel and the phases were
                  separated. The aqueous layer was extracted with ethyl acetate (3   20 mL).
                  The combined organic layers were dried over magnesium sulfate, filtered
                  and concentrated using a rotary evaporator to give a crystalline solid
                  (2S,3R)-epoxychalcone (90 %).
                    The ee (95±99 %) was determined by HPLC (Chiralpak 1  AD column,
                  flow 1 mL/min, eluent ethanol±n-hexane 1:9); (2R,3S)-enantiomer: R t
                  13.6 min, (2S,3R)-enantiomer: R t 20.5 min.
                    1
                     H NMR (200 MHz, CDCl 3 ): d 7.3±7.6, 7.9±8.0 (2m, 10H, Ph); 4.24 (d, J
                  2.0 Hz, 1H, H a ); 4.02 (d, J 2.0 Hz, 1H, H b ).
                                  ÿ1
                    IR (CHCl 3 , cm ): 3069 (C±H epoxide), 3012, (C±H aromatic), 2965,
                  1692 (CˆO), 1599, 1581, 1450 (CˆC), 1406 (C±C aromatic), 1260, 1203
                  (C±O±C), 1098, 1009, 884.
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