Chemistry Reference
In-Depth Information
CO
2
Me
MeO
2
C
O
N
H
CH
3
R
= CN
CH
2
NH
2
CH
2
NHCHO
2
NC
R
N
H
MeO
2
C
CO
2
-t-Bu
1636
CO
2
Me
The same method has been applied in the synthesis of the western building block
1636 of vitamin B
12
, relevant to vitamin B
12
biosynthesis. The original cyano group
is reduced to an amino group, this is formylated, the resulting formamide is de-
hydrated with phosphoryl chloride forming the isocyanide, which is reductively
cleaved [1221]. For the dehydration of the formamide with phosphoryl chloride,
1,8-bis(dimethylamino)naphthalene was chosen as an auxiliary base.
Phosphorus pentachloride
Also interesting in the field of physiologically active substances are phosphorylated
imidazoles 1640. These can be prepared from an isocyanide intermediate 1639
with primary amines, while reaction of the isocyanide with hydrazonic acid yields
phosphorylated tetrazole 1641. The phosphorylated isocyanide 1639 is obtained by
dehydration of the corresponding formamide 1637 with phosphorus pentachloride
via an imine intermediate 1638 [1222].
O
(EtO)
2
P
N
R-HN
N
53-73 %
1640
R
R-NH
2
O
O
O
P(OEt)
2
PCl
5
P(OEt)
2
Et
3
N
P(OEt)
2
Cl
3
C
Cl
3
C
Cl
2
C
83 %
1639
NH-CHO
N=CH-Cl
NC
1637
1638
HN
3
O
P(OEt)
2
Cl
2
C
53 %
1641
N
N
N
N
