Chemistry Reference
In-Depth Information
The synthesis of 1-oxa-3,8-diazospiro[4,5]decan-2-ones 749 from 4-pyridones by
addition of trimethylsilyl cyanide, reduction with LAH, and cyclization of the thus
obtained amino alcohol with triphosgene has been reported [538]. 1-Oxa-3,8-diazo-
spiro[4,5]decan-2-ones are structurally related to the antihypertensive agent Indor-
amine, a known postsynaptic a
1
adrenoceptor blocker.
O
O
OH
(CCl
3
O)
2
CO
(CH
2
)
n
N
(CH
2
)
n
N
CH
2
Cl
2
, rt, 2h
NH
NH
2
748
749
n = 1 yield 72 %
n = 2
Typical procedure. 8-Benzyl-1-oxa-2-oxo-3,8-diazospiro[4,5]decane 749 (n
1) [538]:
Triphosgene (0.12 g, 4.0 mmol) in dry dichloromethane (10 mL) was added drop-
wise to a stirred solution of amino alcohol 748 (n
¼
1) (0.99 g, 4.1 mmol) in di-
chloromethane (25 mL) at room temperature over a period of 2 h. The reaction was
then quenched by the addition of 1% aq. NaOH (20 mL), and the organic layer was
washed with water and dried (MgSO
4
). Removal of the solvent under reduced
pressure gave 749 as a solid (0.801 g, 72%).
6-Methoxybenzoxazolin-2(3H)-one 752 (MBOA; 6-methoxy-2-oxo-2,3-dihydro-
benzoxazole) has been found in extracts of plant tissues from gramineous plants
such as Coix lachryma-jobi, wheat, and maize, and is implicated as a chemical
resistance factor against fungi and insects. Because MBOA is only available in
rather small amounts by plant extraction, several methods have been developed for
its chemical synthesis. The most representative synthetic route involves the inser-
tion of a C
¼
O unit between the amino and hydroxy groups of 2-amino-5-methoxy-
phenol 751, a very easily oxidizable substance.
b
MeO
OH
MeO
OH
H
2
, Pd-C
THF, rt
NO
2
NH
2
750
751
0.33 equiv
(CCl
3
O)
2
CO
2 equiv Et
3
N, THF, rt,
30 min
MeO
O
O
H
75 %
752
O unit have included phosgene (only 15%
yield) [539], ethyl chloroformate [540, 541], urea at elevated temperatures [542-
Compounds used for delivering the C
b
