Chemistry Reference
In-Depth Information
Pivaloyl chloride is a key starting material for the preparation of many pesticides,
such as the selective herbicide Oxadiazon, prepared according to a process dis-
closed by Rhˆne-Poulenc [222]. Phosgene reacts with the intermediate hydrazide to
afford the 1,3,4-oxadiazolinone.
Cl
Cl
Cl
Cl
Cl
O
H
N
NH
2
t
Bu
Et
3
N, toluene
Pr
i
O
Pr
i
O
N
N
H
H
O
toluene
110°C
COCl
2
Cl
Cl
N
t
Bu
Pr
i
O
N
O
O
Oxadiazon
2,2
-Carbonyl-bis(3,5-dioxo-4-methyl-1,2,4-dioxazolidine) (acronym: COMODD), a
symmetrical non-hygroscopic equivalent of 1,1
O
-carbonyldiimidazole (CDI) [223],
has been employed for the synthesis of the insecticide Aldicarb in 85% yield,
avoiding use of the noxious isocyanate [224] and following a proven general reac-
tion route for this phosgene equivalent.
O
O
O
O
O
O
O
R
1
R
2
NH
2
O
N
R
1
R
2
N
N
+
R
1
OH
NMe
NMe
O
N
MeN
O
O
O
H
O
O
O
85-90 %
COMODD
O
ALDICARB =
O
N
H
S
The reaction of phosgene with cyanohydrazines to yield 3-hydroxy-5-chloro-1,2,4-
triazoles has been applied in the synthesis of the key intermediate 296 in the pro-
duction of the soil-applied nematocide Isazofos [225].
An alternative synthetic route to the above intermediate 296, avoiding the ex-
tremely noxious cyanogen chloride, has also been disclosed [226].
a-Chloroethyl chloroformate (''ACE-Cl'', see Section 4.7.2) has been successfully
used for the selective N-dealkylation of tertiary alkylamine intermediate 297 in a
