Abstract
The enantioselective synthesis of sterically congested
C
2-symmetric 1,2-di-
tert-butyl and 1,2-di-(1-adamantyl)ethylenediamines was successfully achieved starting from the simple heterocycle, 2-imidazolone.
An enantioselective synthesis of sterically congested 1,2-di-
tert-butyl and 1,2-di-(1-adamantyl)ethylenediamines has been developed. Thus, diastereomerically pure
trans-1-apocamphanecarbonyl-4,5-dimethoxy-2-imidazolidinones
6
and
7
were successfully prepared by optical resolution of (±)-
trans-4,5-dimethoxy-2-imidazolidinone using apocamphanecarbonyl chloride (MAC-Cl) followed by stereospecific and stepwise substitution of the dimethoxyl groups using
tert-butyl or 1-adamantyl cuprates to provide (4
S,5
S)-4,5-di-
tert-butyl and (4
R,5
R)-4,5-di-(1-adamantyl)-2-imidazolidinones
12
and
15
, respectively. Furthermore,
N-acetyl 4,5-di-
tert-butyl and 4,5-di-(1-adamantyl)-2-imidazolidinones
16a,
b
were enantioselectively deacetylated using a catalytic oxazaborolidine system to provide enantiopure 1-
p-tolylsulfonyl-4,5-di-
tert-butyl-2-imidazolidinones
12
and
19
and 1-
p-tolylsulfonyl-4,5-di-(1-adamantyl)-2-imidazolidinones
18
and
20
, respectively. Finally,
N-
p-tolylsulfonyl-2-imidazolidinones
12
and
15
were treated with 30
equiv of Ba(OH)
2·8H
2O to achieve ring cleavage and to provide (1
S,2
S)-1,2-di-
tert-butylethylenediamine
3
and (1
R,2
R)-1,2-di-(1-adamantyl)ethylenediamine
4
.