Chemistry Reference
In-Depth Information
is redissolved in tetrachloromethane/petroleum ether, and the resulting solution is
placed in a refrigerator until crystals appear. Yields of 922 are 68-92%.
O
1.
CDI
OH
OH
CH
2
Cl
2
O
O
R
1
= H, alkyl aryl, aralkyl
R
2
= alkyl, aralkyl
68-92 %
N
R
1
R
2
N
30-60 sec
2. HCl
0°C
R
1
R
2
O
O
921
922
40°C 60 min
imidazole,
product dependent on R
1
and R
2
R
2
R
1
R
1
R
2
O
O
H
N
N
R
1
R
2
H
O
O
OH
O
O
O
923
924
In a taxoid synthesis, a cyclocarbonylation is performed with CDI at the 2- and 3-
positions of the taxol ring system 925, prior to closure of the eight-membered B
ring, giving 926 in 95% yield [662].
TBSO
TBSO
OTBS
OTBS
CDI
(10 equiv.)
MeCN
reflux, 2 h
O
H
O
O
95 %
OH
925
926
O
A special type of iodolactonization is the iodocarbonate cyclization of homoallylic al-
cohols 927 [663]. Iodocarbonate cyclization is an e
cient and moderately erythro-
stereoselective method for the functionalization of homoallylic alcohols with rela-
tive 1,3-asymmetric induction.
Typical procedure. (4-Methoxyphenyl)methyl 1-(2-propenyl)-4-pentenyl carbonate 928
[663]: A solution of CDI (970 mg, 6 mmol) and 4-methoxybenzyl alcohol (830 mg,
6 mmol) in THF (10 mL) was kept at 21
C for 1 h. 1,7-Octadien-4-ol 927 (768 mg)
was then added, and the solution was heated to 60
C for 16 h. After cooling and
dilution with diethyl ether (40 mL), the mixture was washed with water (2
40
mL) and saturated NaCl solution (40 mL), dried (magnesium sulfate), concen-
