Chemistry Reference
In-Depth Information
Ph
Ph
N
N
N
N
(CCl
3
O)
2
CO
N
H
THF
O
O
OH
742
743
Typical procedure. 2-Phenyl-1,2,4-triazolo[1,5-c][1,3]benzoxazin-5-one 743 [535]:
Tri-
ethylamine (0.42 mL) and triphosgene (0.15 g) were added to a solution of 3-phenyl-
5-(2-hydroxyphenyl)-1,2,4-triazole (1.26 mmol) in anhydrous tetrahydrofuran
(10 mL). The mixture was stirred at room temperature for 9 days. On the third and
sixth days further triethylamine (0.42 mL) and triphosgene (0.15 g) were added.
The mixture was eventually diluted with water and the resulting solid was collected
and washed with water. Yield 93%.
The relative syn/anti stereochemistry of amino alcohols 744a,b has been assigned
by analysis of the J
4;5
coupling constants of the oxazolidin-2-ones prepared with
triphosgene, thereby allowing the configuration of the nitrogen-substituted stereo-
genic center to be unambiguously established [536].
O
H
Ph
N
O
Ph
N
OTBDPS
OTBDPS
HH
OH
a
a
(CCl
3
O)
2
CO
O
H
NEt
3
, CH
2
Cl
2
, 0°C
Ph
N
Ph
N
O
OTBDPS
OTBDPS
OH
HH
b
744
b
745
TBDPS = tBuPh
2
Si-
The preparation of oxazolo[5,4-b]pyridin-2(1H)-one 747 from the readily available
3-amino-2-pyridone 746 with triphosgene or CDI at
78
C has been reported
[537].
H
N
NH
2
(a) or (b)
O
O
N
N
H
O
746
747
(a)
(CCl
3
O)
2
CO
, CH
2
Cl
2
/THF (1:1 v/v), 6 h, Et
3
N, 78 % or DBU
(b)
CDI
, CH
2
Cl
2
/THF (1:1 v/v), 6 h, DBU, 50 %
