11.19 ANTI HYDROXYLATION OF ALKENES VIA EPOXIDES
- Epoxidation of cyclopentene produces 1,2-epoxycyclopentane:
H H
HH
O
O
Cyclopentene 1,2-Epoxycyclopentane
+ ROC
O
H + ROC
O
H
- Acid-catalyzed hydrolysis of 1,2-epoxycyclopentane yields a trans-diol,
trans-1,2-cyclopentanediol.
HH
O O+
H
O
H
+ O
O
O H
O
H
H
+ +
H O H
H
HH
H
H
H H
trans-1,2-Cyclopentanediol
+
H
H H
H
O
Henantiomer
1) Water acting as a nucleophile attacks the protonated epoxide from the side
opposite the epoxide group.
2) The carbon atom being attacked undergoes an inversion of configuration.
3) Attack at the other carbon atom produces the enantiomeric form of
trans-1,2-cyclopentanediol.
- Epoxidation followed by acid-catalyzed hydrolysis constitutes a method for anti
hydroxylation of a double bond.
