Level 2 – Case 27
182
3H +
N
MeO
OMe
H
Figure 27.3
In Summary
The E/Z isomerization of C=N bonds can occur either by a nucleophile catalysis
mechanism or by iminium ion rotation. The electrophilicity and the barrier to rotation of the iminium ion formed during the first step of the reaction determine the
isomerization pathway. Thus, hydroximoyl chlorides 1 and 2 isomerize only by
the nucleophile catalysis mechanism whereas hydroximates 3 are capable of isomerizing by iminium ion rotation.
A Ad dd di it ti io on na al l C Co om mm me en nt ts s
This problem is based on the work by Johnson JE, Morales NM, Gorczyca AM,
Dolliver DD, McAllister MA (2001) J. Org. Chem. 66:7979-7985.
S Su ub bj je ec ct ts s o of f R Re ev vi is si io on n
Nucleophile catalysis. Bond rotation energy barriers.
182
3H +
N
MeO
OMe
H
Figure 27.3
In Summary
The E/Z isomerization of C=N bonds can occur either by a nucleophile catalysis
mechanism or by iminium ion rotation. The electrophilicity and the barrier to rotation of the iminium ion formed during the first step of the reaction determine the
isomerization pathway. Thus, hydroximoyl chlorides 1 and 2 isomerize only by
the nucleophile catalysis mechanism whereas hydroximates 3 are capable of isomerizing by iminium ion rotation.
A Ad dd di it ti io on na al l C Co om mm me en nt ts s
This problem is based on the work by Johnson JE, Morales NM, Gorczyca AM,
Dolliver DD, McAllister MA (2001) J. Org. Chem. 66:7979-7985.
S Su ub bj je ec ct ts s o of f R Re ev vi is si io on n
Nucleophile catalysis. Bond rotation energy barriers.