Page 143 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

130 hydrolysis, oxidation and reduction

. One 500 mL Erlenmeyer flask
. One Bu Èchner funnel, diameter 10 cm
. One Bu Èchner flask, 500 mL
. Filter paper
. One 500 mL separatory funnel
. One glass column, diameter 7 cm
. One Dewar flask
. Rotary evaporator

Procedure
1. Diethyl tartrate (10 g, 47.5 mmol) was placed in a 100 mL round-bottomed
flask equipped with a magnetic stirrer bar, under nitrogen. Dry diethyl ether
(30 mL) was then added and the mixture was cooled at 0 8C. To this solution,
ortho-periodic acid (10.8 g, 47.5 mmol) was added carefully, portionwise,
over 20 minutes and the resulting mixture was vigorously stirred for 1 hour
under nitrogen at the same temperature.
2. Activated molecular sieves (7 g) were added to the reaction and stirring
continued for 20 minutes.
3. The mixture was carefully filtered into a 250 mL round-bottomed flask
through a thin pad of Celite. The filtration was completed by rinsing the
packing with diethyl ether (50 mL).
4. The solvent was removed from the filtrate using a rotary evaporator to
afford the corresponding ethyl glyoxylate (9.7 g, 95 mmol)
5. In the 250 mL round-bottomed flask equipped with a magnetic stirrer bar,
the resulting ethyl glyoxylate (9.7 g) was placed under nitrogen. Dry methyl-
ene chloride (125 mL) was added followed by activated molecular sieves
(10 g). The mixture was then cooled at 0 8C under nitrogen.
6. To this solution (S)-(ÿ)-phenylethylamine (12.4 mL, 95 mmol) was added
dropwise and when the addition was complete, stirring was continued for
1 hour at 0 8C.
7. The mixture was cooled to ÿ788C in a dry ice±acetone bath and trifluor-
oacetic acid (7.4 mL, 95 mmol), boron trifluoride etherate (12.1 mL,
95 mmol) and freshly distilled cyclopentadiene (6.2 g, 95 mmol) were added
in that order over a 20 minute period. The mixture was stirred at ÿ788C for
5 hours before it was allowed to warm to room temperature.
8. The reaction was hydrolysed and neutralized (pH ˆ 8) in a 500 mL Erlen-
meyer flask with a saturated aqueous solution of sodium bicarbonate.
9. The resulting mixture was filtered into a Bu Èchner funnel with the aid of a
water aspirator and transferred to a 500 mL separatory funnel where the
phases were separated. The aqueous layer was extracted with methylene
chloride (2 150 mL). The combined organic layers were dried over mag-
nesium sulfate, filtered and concentrated using a rotary evaporator to give
the corresponding mixture of crude Diels±Alder adducts (minor exo-isomer
‡ major endo-isomer ‡ major exo-isomer. Exo/endo ratio: 98/2).