Stereoselective Synthesis of 2-Acylaziridines 209
In Summary
We can conclude that 2-acylaziridines 4 can be obtained from Z-(2-acetoxyvinyl)iodonium bromides 1 and imines 3 in the presence of EtOLi. The reaction is
a stepwise process. During the first step a monocarbonyl iodonium ylide 2 is
formed by removal of the acetate group promoted by EtOLi. The second step consists in the nucleophilic attack of the ylide 2 to the imine C=N bond to yield a
zwitterion intermediate (rate-determining step) that leads to the aziridine 4 by
means of an intramolecular S N 2 reaction. The overall mechanism could be drawn
as in Scheme 31.11. Although the aziridines 4 are obtained as cis:trans mixtures,
the stereochemical outcome of the reaction can be controlled by the reaction solvent and by the substituent on the nitrogen atom in the imines.
I(Ph)Br
AcO
R
EtOLi
R
IPh
O
R 1 CH NR 2
R
O
IPh
R
1
NR
2
N
R 1
R
O
R 2
1
2
4
fast
slow
Scheme 31.11
Additional Comments
This problem is based on the work by Ochiai M, Kitagawa Y (1999) J. Org.
Chem. 64:3181-3189.
Subjects of Revision
Solute-solvent interactions. Empirical parameters of solvent polarity.