Level 1 – Case 6
34
O
SPh
R
H
H
O
R
SPh
H
H
CH 2 Cl 2 , -30 o C
1) Me 3 Al (3 equiv)
R
S Ph
OH
Me
R
S Ph
OH
Me
3
1
4
2
R = C 3 H 7 , C 6 H 13 , BnOCH 2
2) 3M HCl
CH 2 Cl 2 , -30 o C
1) Me 3 Al (3 equiv)
2) 3M HCl
Scheme 6.1
Experimental Data
When 2,3-epoxy amine 5, structurally related to epoxyalkanes 1 and 2 was treated
with trimethylsilyl trifluoromethanesulfonate (TMSOTf) in CDCl 3 at – 40°C, and
the reaction mixture was allowed to warm to room temperature, the
1
H-NMR
spectrum of the resulting solution clearly showed the formation of a new compound 6, stable at room temperature (Scheme 6.2). Compound
t t
6 was very reactive
in the presence of nucleophiles yielding, after hydrolysis, products with the structure of aminoalcohols.
O
N
H
H
Pr
CH 2 Ph
CH 2 Ph
H
PhH 2 C
OTMS
Pr
N
CH 2 Ph
TfO
6
TMSOTf, CDCl 3
-40
o C
5
Scheme 6.2
Discussion
It is evident that the reaction of epoxides 1 and 2 with Me 3 Al is not a simple epoxide ring-opening by nucleophilic attack at the C2 position. As shown in Scheme
6.3, the expected S N 2 backside nucleophilic attack at C2 in cis-epoxide 1 would
yield 7, which has inverted the configuration at C2 during the process. After