Synthesis of auxinic herbicide Dicamba, from Unger: Pesticide Synthesis Handbook

1. Carboxylic Acids 789
Dicamba
Uses : herbicide for maize, sorghum, sugar cane, pastures
Trade names: Banvel, Mediben (Sandoz)
Type: halogenated aromatic carboxylic acid
Synthesis:
CI
CI
CI
+ NaOH >
CI
~ OH
Cl
2.5 dichloro
phenol
1.2.4 trichloro
benzene
CO2
C1
~ --O--~--
_C.~0
'o-~-C1
~H20
Cl
C ~
Cl OH
I
0 O-C-
/ t
S
0 O-C-
l
dimethyl
sulfate
IKOH
CI
~ OH
C ~,.0
CI "OK
dicamba

2. 790 Pesticides Synthesis Handbook
alternate routes :
(i)
Cl
o OH
c
3.6 did%loro
benzoic acid
l
--c--o o
S
,/%
--C--O O
I
NaGH
dicamba
(ii)
c
1
NaNO2
HCl
OH
~c /
Cl ~ N= N-- Cl
3.5 did~loro
anthranilic
acid
Io OH
%/
c
Cl
methvl d%loride
I
-- c-- C1 or
I
dimethylsulfate
Idicamba

3. Carboxylic Acids 791
(iii)
l
--C--
Cl ~ Cl
Cl
2.3.6 triahloro
toluene
+ HNO3
o OH
%/c
Cl ~~Cl
>
Cl
2.3.6 trichloro
benzoic acid
I
--~- o-Na
sodium
methylate
) dicamba
(iv)
OH
I
Br C1
(v)
Cl
Br
OH
--c-
Cl
+ KOH
e-
e ..
OH
I
--C--
Ci~cl c'-
l
-?~s~~
-~" %oI
OH
I
--C--
ClOH/ci
~MNO4
or
Pt/Pd
NaOH
dicamba