Chemistry Reference
In-Depth Information
N
N
N
N
55 %
1701
54 %
1702
H
O
2
N
O
2
N
N
N
O
2
N
N
N
H
S
S
H
F
F
DBU
73 %
1706
56 %
1703
AcHN
CO
2
Me
AcHN
CO
2
Me
1705
1704
H
NO
2
H
3
C-NO
2
N
S
N
S
N
N
NaH
DMF
H
H
O
O
1708
52 %
1707
room temperature and the residue is extracted four times with petroleum ether
(40-60
C). After evaporation of the solvent, the residue is fractionated. Carbodi-
imides are identified by their
1
H NMR spectra and boiling points.
PPh
O
O
CBr
4
Et
3
N
N
Bn
H
2
N-Bn
H
NH-Bn
N
H
CCl
3
CH
2
Cl
2
-20°C
or rt
Ph
Ph
Ph
92 %
1710
99 %
1711
1709
N-Bn
H
2
N-Bn
H
NH-Bn
Yb(OTf)
3
THF/H
2
O
9:1
Ph
89 %
1712
Among many naturally occurring compounds, such as tetrodotoxin, the guanidi-
nium group plays an important role in expressing biological activity due to its cat-
ionic nature. It can be directly prepared from trichloroacetamide 1709 via allyl
benzyl urea 1710 by dehydration with triphenylphosphine/tetrabromomethane and
triethylamine at room temperature or
20
C affording carbodiimide 1711 in 99%
