Chemistry Reference
In-Depth Information
An intense research effort was dedicated to finding new synthetic routes and cata-
lysts or improved processes for obtaining carbamates and ureas, avoiding the
hazardous phosgenation conditions. For example, SNPE reported the use of hexa-
methylguanidinium chloride hydrochloride (HMGCl
.
HCl) as a catalyst, which is
soluble during the reaction, but insoluble after its completion and thus can be re-
moved by simple filtration, for the synthesis of high quality n-octyl thiochlorofor-
mate. This thiochloroformate is a useful intermediate in the manufacture of the
herbicide Pyridate (Lentagran
2
, Chemie-Linz AG) [211].
O
COCl
2
SH
S
l
HMGCl * HCl
Cl
N
N
S
O
O
Pyridate
2-Chloronicotinyl isocyanate has been used to prepare interesting new insecticides
such as 292, which are effective against larvae, especially from lepidoptera [212,
213].
O
Cl
Cl
NCO
+
H
2
N
O
CF
3
N
l
N
Cl
20°C
DCE
Cl
Cl
O
O
O
N
N
H
N
H
Cl
CF
3
N
l
68 %
292
Chloroformates are valuable raw materials for a series of crop protection agents.
The carbamic fungicide Propamocarb is prepared with n-propyl chloroformate.
H
N
O
l
N
O
N
NH
2
+
O
O
Propamocarb
