Aziridine Essay

Name _____________________
Page 1
I. (19 points)
A. Aziridines are 3-membered nitrogen heterocycles that can behave as electrophiles in substitution reactions.
The aziridine 1 shown below has been shown to react with Na+ –OCH3 to give products 2 and 3.
Ph =

Note:

Na
N

OCH3

Br

N

+

N
OCH3

3

2

1

This abbreviation has been used in the scheme below. You may also use this abbreviation when drawing
Newman projections on page 5.

OCH3

(a) The formation of product 3 occurs via (i) reaction between CH3O– and the more substituted carbon of aziridine 1 to generate intermediate 4; (ii) intramolecular nucleophilic substitution to generate product 3.
Provide the structure of intermediate 4 and draw curved arrows showing the
The ratio of 8 and 9 depends on the type of base that is used.
H

O

H

H

O

CH3 +

Li

H

B

Li
CH3

+ HB

H

H

Li

O

CH3

+

+ HB

2-methylcyclohexanone

Note: B is a generic base and HB is its conjugate acid.
Specific bases are given in parts b and c below. 8
9
(a) Based on the information provided below, construct an energy diagram for the conversion of
2-methylcyclohexanone + base (SM) to products 8 and 9 . On your diagram, clearly show the position of products 8 and 9, transition states A and B, and draw the appropriate energy curves.
SM

• The reaction occurs in a single step.
No intermediates are formed
• The conversion of SM to 8 proceeds through transition state A.
• The conversion of SM to 9 proceeds through transition state B.
!G° for SM
!G° for SM
!G‡ (EA) SM
!G‡ (EA) SM

2 kcal/mol

B
A

!G
(kcal/mol)

SM

8: –2 kcal/mol
9: –4 kcal/mol
A: +4 kcal/mol
B: +8 kcal/mol

8
9

Progress of Reaction

(b) When Li+ –N[CH(CH3)2]2 is used as a base, the product ratio is controlled by reaction kinetics. Which is the major product under these conditions (circle one