Chemistry Reference
In-Depth Information
5-Substituted 2-chloropyridines, useful intermediates for the synthesis of valuable
insecticides, have been prepared by Vilsmeier formylation of substituted enamides
300 and subsequent N-debenzylation [229, 230].
DMF
Cl
N
N
l
+
2
+
100°C, 12 h
+ Me
2
NH*HCl
+ DMF
+ HCl
N
l
O
Cl¯
301
300
The modified reaction of Vilsmeier salt 301 with acetals has been employed for a
new synthesis of 1,4-dimethylpyrazole [231]. Chlorination of 1,4-dimethylpyrazole
with chlorine in 1,2-dichloroethane affords 3,5-dichloro-1,4-dimethylpyrazole in
high yield [232], the key starting material for the synthesis of pyrazolesulfonyl urea
302, useful as broad spectrum, pre- and early post-emergence herbicides such as
NC-319 [233].
Cl
O
MeNHNH
2
solvent
90 °C, 4h
N
O
+
N
l
N
Cl
N
75-80°C
O
89 %
Cl
301
Cl
COOMe
N
SO
2
HN
N
H
N
N
OMe
O
N
302
NC-319
OMe
Herbicidally active 1-aryl-4-carbamoyl-tetrazolinones 304 were recently obtained by
reacting 1-aryl-tetrazolinones with phosgene in the presence of a solvent at 0-
150
C, and then reacting the resulting (novel) 1-aryl-4-chlorocarbonyl-tetrazolinones
303 with amines in the presence of a solvent, and, where appropriate, in the pres-
ence of a further basic compound, at
100
C [234].
20 to
þ
O
O
O
O
O
HNR
1
R
2
R
1
COCl
2
Ar
Ar
Ar
N
Cl
N
N
NH
N
N
N
N
N
N
solvent
0-150°C
R
2
N
N
N
303
304
R
1
, R
2
= alkyl, alkenyl, alkynyl, alcoxy
Ar = phenyl,naphtyl
Thriotrone herbicidal agents 307 having substituted cyanuric structures [e.g. 1-(3-
