Organic Chemistry

Section 12.8 Arene Oxides 457

Epoxides are synthetically useful reagents because they can react with a wide variety

of nucleophiles, leading to the formation of a wide variety of products.

Epoxides also are important in biological processes because they are reactive

enough to be attacked by nucleophiles under the conditions found in living systems

(Section 12.8).

Notice that the reaction of cyclohexene oxide with a nucleophile leads to trans

products because an reaction involves back-side nucleophilic attack.

PROBLEM 17

Why does the preceding reaction form two stereoisomers?

PROBLEM 18

Give the major product of each of the following reactions:

a. c.

b. d.

PROBLEM 19

Would you expect the reactivity of a five-membered ring ether such as tetrahydrofuran

(Table 12.2) to be more similar to an epoxide or to a noncyclic ether?

12.8 Arene Oxides

When an aromatic hydrocarbon such as benzene is ingested or inhaled, it is enzymati-

cally converted into an arene oxide. An arene oxideis a compound in which one of the

“double bonds”of the aromatic ring has been converted into an epoxide. Formation of

an arene oxide is the first step in changing an aromatic compound that enters the body

as a foreign substance (e.g., cigarette smoke, drugs, automobile exhaust) into a more

water-soluble compound that can eventually be eliminated. The enzyme that detoxifies

aromatic hydrocarbons by converting them into arene oxides is called cytochrome P 450.

CH 3 O−

CH 3 OH

H C

H 3 C

CH 3

CH 3

O

CH 3 O C

−

H 2 C CH 3 OH

CH 3

CH 3

O

C

H C

H 3 C

H+

CH 3 OH

CH 3

CH 3

O

H 2 C CH^3 C

CH 3

O

C

H+

CH 3 OH

SN 2

+ CH 3 CHCH 2 NH 2 CH 3

O−

CH 3 CH CH 2

O

CH 3 CHCH 2 NHCH 3

OH

CH 3 NH 2

+

H+

H 2 CCH 3 C

CH 3

CH 3 CH 3

C− CH 3 C

O−

CCH 2 CCH 3

CH 3

CH 3 C

OH

CCH 2 CCH 3

O

C +

− H+

CN

C

−O

NC

OH

N OH

CN

O

+ +

O−

CN

+

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