FORM 2
THE PATENTS ACT, 1970

COMPLETE SPECIFICATION
[SEE SECTION 10]

A Process For the Preparation of Lambda Cyhalothrin with High Purity of the Required Isomer

RALLIS INDIA LIMITED UNDER THE INDIAN REGISTERED OFF:ICE DINSHAW VACHHA 020. MAHARASHTRA
, AN INDIAN COMPANY REGISTERED
COMPANY'S ACT, 1956 HAVING ITS
AT "APEEJAY HOUSE" 7TH FLOOR,
ROAD, CHURCH GATE, MUMBAI - 400
, INDIA

The following this invention
specification particularly describes and ascertains the nature of and the manner in which it is to be performed.

1

Field of Invention

This invention relates to Cyhalothrin. The lambda invention has the formula
an improved process for the preparation of Lambda Cyhalothrin prepared by the process of the present I given below

The process is applicable industrially with a very high
for the economic production of lambda cyhalothrin purity.

Lambda Cyhalothrin is a non-systemic insecticide with contact and stomach action and repellant properties. It gives a rapid knock down and long residual activity. It is used to central a wide variety of insect pests like aphids, thrips, Lepidoptera larvae, Coleoptera larvae and adults in cereals, ornamentals, potatoes, vegetables, cotton and other crops. It provides very good control of insect borne plant viruses and also used for control of insect pests in public health.
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Lambda Cyhalothrin Phenoxy benzyl - (Z)
- dimethyl cyclopropan
- (1S) - cis - 3
cyclopropane carboxylase
exists as an enantiomeric mixture of (S) a - cyano-3-
(1R) - cis - 3- (2-Chloro - 3,3,3 - trifluoro propenyl) 2,2
carboxylate and (R) - a - cyano-3-Phenoxy benzyl - (Z)
(2-Chloro - 3,3,3 - trifluoro propenyl) 2,2 - dimethyl

Cyhalothrin exists in 4 isomeric forms namely:

The ester derived from The ester derived from The ester derived from

(+) cis acid and a - (S) - alcohol [ISOMER 1] [-) cis acid and a - (R) - alcohol [ISOMER 2] ■;+) cis acid and a - (R) - alcohol [ISOMER 3]

The ester derived from (-) cis acid and a - (S) - alcohol [ISOMER 4]

The isomers 1 and 2 another enantiomeric pair
from one enantiomeric pair and the isomers 3 and 4 form

It has been established

by extensive research that isomer 1 is only insecticidally

active and the other isomers are practically inactive
The process for the preparation of lambda cyhalothrin is reported in Indian Patent Number 178538 in which costly solvents like 1,4 - Diazabicyclo (2,2,2) octane. Lambda cyhalothrin prepared by this process is not economical and cannot be employed for large-scale preparation of this material. Also this process leads to lot of side reactions aim the required isomer is not obtained in higher purities. This process also leads to an extra operation of crystallization in order to get high pure material. With an aim to obtain a product, which predominantly contains the required isomer of higher purity, and with reagents, which are easily available, and a process, which can avoid the crystallization step, the present process was developed.
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Objectives of the invention

The main objective of preparation of Lambda insecticidally active isomer -alcohol [ISOMER 1]
this invention is to provide an improved process for the
Cyhalothrin, which predominantly contains the
namely the ester derived from (+) cis acid and a - (S)

Another objective of the present invention is to provide an improved process for

the preparation of pure
Another objective of the the preparation of lambda are easily available.

lambda cyhalothrin, which can be applied commercially.

present invention is to provide an improved process for cyhalothrin, which employs the use of reagents, which

Yet another objective of
for the preparation of lambda
: the present invention is to provide an improved process cyhalothrin in which the yields are high (86 %).

Still another objective of for the preparation of isomer is above 95%.
the present invention is to provide an improved process lambda cyhalothrin in which the purity of the required

Still another objective of the present invention is to provide an improved process for the preparation of lambda cyhalothrin, which will avoid the extra operation of crystallization.
Description of the Invention

Accordingly the present lambda cyhalothrin, stomach action and
invention provides a process for the preparation of
which is a non-systemic insecticide with contact and
repellant properties. It gives a rapid knock down and long

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residual activity. It is used to control a wide variety of insect pests like aphids, thrips, Lepidoptera larvae, Coleoptera larvae and adults in cereals, ornamentals, potatoes, vegetables, cotton and other crops. It provides very good control of insect borne plant viruses and also used for control of insect pests in public health.
The process for the preparation of lambda cyhalothrin involves the epimerization of cis cyhalothrin to Lambda cyhalothrin. Cis Cyhalothrin, initially taken for the reaction contains isomers 1 & 2 in 42 - 44 % and isomers 3 & 4 in 56 - 58 % and with combined purity of more than 96 %.
in hydrocarbon solvents like n-Heptane, n - Hexane, n-more preferably n - Hexane. The solvent is taken in an he molar equivalent of cis cyhalothrin charged. The
Cis cyhalothrin is taken Octane or n - Nonane amount 2 - 5 times

epimerization reaction mass is cooled to - 0.5°C to - 10° C by ice salt mixture.

The epimerization react amines like Morpholine amine. More preferably
The epimerization reac isopropyl amine, which process, which Isopropyl amine
The addition of the co and avoids additional

ion is catalyzed by the presence of organic secondary , Piperidine, N - Methyl benzyl amine, and Diisopropyl 7\ Di isopropyl amine.

tion is hastened by the addition of small quantities of
is used as a co base this is a unique addition in the
supplements the addition of Di isopropyl amine. The addition of
increases the efficiency of the process and reduces the cost.
base also improves the isomer ratios in the process itself
operation of crystallization.

The amount of organic amine used in the epimerization reaction is in the range of 0.4 to 0.6 molar equivalents of cis cyhalothrin used. More preferably in the range of 0.5 to 0.6 moles.

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The co base employed equivalents to cis cyhalothrin moles.
in the reaction is in the range of 0.2 to 0.5 molar used. More preferably in the range of 0.3 to 0.4

The reaction is
portion of pure lambda seeding is 1/6th Preferably in the range
maintaidied at - 20°C and then the reaction is seeded with a small cyhalothrin. The amount of pure material added for

1/12 molar equivalents of initial cis cyhalothrin used.
f 1/81 to 1/10 amount of cis cyhalothrin used.

The reaction is maintained at -20°C for 24 hours using a cryogenic bath employing isopropyl alcohol or methanol as cooling media and then the reaction mass is analyzed for completion of the reaction. When the conversion reaches
95% the reaction mass is cooled to -30° C and maintained at that temperature
for 6 hours
After the completion of 6 hours the reaction mass is filtered at - 30 C. At this
stage the product contains isomers 1 & 2 in the ratios 94 - 95 : 6 - 5 and the

product is washed with isomer ratios to 96 - 97
cold hexane at - 5°C. This hexane wash improves the : 4 - 3. The purity of the product before the hexane wash

is in the range of 93 - 94 % and after hexane washes the purity goes up to 95 -96 %. The product is the n dried at room temperature under vacuum.

The mother liquor obtained batches without affecting from the process. This
from the process is recycled in the subsequent the quality and the quantity of the material obtained makes the process environment friendly.

The details of the invention provided to illustrate the limit the scope of the i invention.
are given in the examples given below which is
invention only and therefore should not be construed to
invention following examples do not limit the scope of the

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Example 1
Preparation of Lambda Cyhalothrin
The reaction is cooled
filtered
the reaction mass at -
Hexane maintained at
To a 4 necked round bottom flask 225 g of n-Hexane is charged and 125 g of cis cyhalothrin, which contains isomers 1 & 2 in 42 - 44 % and isomers 3 & 4 in 56 -58 % and with combined purity of more than 96 %. is added. The reaction mass is stirred and cooled to - 5°C to - 10°C by using ice -salt mixture. To this 0.5 moles of Diisopropyl amine and 0.35 moles of isopropyl amine as co base is added and the reaction mass is further cooled to - 20°C . After stirring for 30 minutes the reaction mass is seeded with 12 g of pure lambda cyhaothrin which has purity more than 95%. The reaction mass is maintained at - 20 °C for 24 hours and a sample is taken for analysis in order to check the conversion. When the conversion reaches) more than 95%, usually this is attained at 32 - 36 hours.
to - 30°C and maintained for further 5 hours and then
25°C to - 30°C. The product obtained is washed with cold 5°C and the product is dried at room temperature under

vacuum. The mother liquor is recycled in the subsequent batches.

Yield 110 g (87% Yield) Purity : 95.4% of isomer

1

Example 2
To a 4 necked round cyhalothrin which 58 % and with combined stirred and cooled to –
of Diisopropyl amine the reaction mass is reaction mass is seeded
bottom flask 225 g of n-Hexane is charged and 125 g of cis
contains isomers 1 & 2 in 42 - 44 % and isomers 3 & 4 in 56 -
purity of more than 96 %.is added. The reaction mass is
5°C to - 10°C by using ice -salt mixture. To this 0.6 moles
0.5 moles of isopropyl amine as co base is added and
further cooled to - 20°C. After stirring for 30 minutes the
with 12 g of pure lambda cyhaothrin which has purity

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more than 95%. The sample is taken for conversion reaches
reaction mass is maintained at - 20 °C for 24 hours and a Analysis in order to check the conversion. When the
more than 95%, usually this is attained at 32 - 36 hours. The

reaction is cooled to -the reaction mass at -cold Hexane maintained under vacuum. The mo
30 C and maintained for further 5 hours and then filtered
25°C to - 30°C. . The product obtained is washed with at - 5°C and the product is dried at room temperature her liquor is recycled in the subsequent batches.

Yield: 108 g (86% Yield) Purity : 95.8 % of isomer 1

Advantages of the Invention
1. This process consistently gives Lambda Cyhalothrin with the required active isomer 1 of 95 % purity minimum
2. The process is sir simple and can be adapted in plant very easily
3. The process is cost efficient where it employs lesser amount of Di
isopropyl amine.
isopropyl amine.
4. The process is Unique because of the addition of Isopropyl amine as co base, which helps in hastening the epimerization reaction and improving the isomer ratios.
5. The process avoids an operation of crystallization which is otherwise laborious and time consuming.
6. The mother liquour obtained from the process can be recycled making the process environment friendly.

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We claim

1. A process for the

preparation of Lambda cyhalothrin of formula I

which is useful

as an insecticide with contact and stomach action and

repellant properties and is used to control a wide variety of insect pests like aphids, thrips, Lepidoptera larvae, Coleoptera larvae and adults, comprises the epimerization of cis - cyhalothrin in hydrocarbon solvents and in presence of organic amines and co bases and seeding the reaction mixture with small quantities of very pure Lambda cyhalothrin at temperatures of -20° C to - 30° C for 24 - 36 hours and washed in an organic solvent at low temperatures to give the insecticidally active isomer namely the ester derived from (+) cis acid and a - (S) - alcohol [ISOMER 1] commonly known as Lambda cyhalothrin of high purity.
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2. A process as claimed n-Heptane, n -Hexane.
in claim 1, wherein the hydrocarbon solvent used is Hexane, n- Octane or n - Nonane more preferably n -

3. A process as claimed in claims 1 and 2, wherein the hydrocarbon solvent the used is 2-5 timed the molar equivalents of cis cyhalothrin taken for the reaction.
4. A process as c Morpholine, Pi
5. A process as is Diisopropyl
6. A process as amine used is
aimed in claim 1 wherein the organic amines used is peridine, N - Methyl benzyl amine, and Diisopropyl amine, claimed in claims 1 and 4 wherein the organic amine used amine.
claimed in claims 1, 4 and 5 wherein the amount of organic in the range of 0.5 to 0.6 molar equivalents of cis
cyhalothrin used.
7. A process as claimed in claim 1, wherein the co base used is Isopropyl amine
range of 0.2 to 0.5 molar equivalents to cis cyhalothrin used, the range of 0.3 to 0.4 moles.
claimed in claim 1, where in the amount of pure material
ng is 1/6,h - 1/12,h molar equivalents of initial cis
Preferably in the range of 1/8,h to 1/10th amount of cis
8. A process as claimed in claims 1 and 7 wherein the amount of co base used is in the
More preferably
9. A process as added for seed
cyhalothrin used cyhalothrin used.

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10. A process as
11. A process as
12. A process as -5°C.
claimed in claim 1 the temperature of the reaction is -25° C. claimed in claim 1 the solvent used for washing is n-hexane claimed in claims 1 and 11 the temperature for washing is

13.A process as claimed in claims 1 -12 wherein the process avoids the crystallization step.
14.A process as claimed in claims 1 -13 the isomers 1 & 2 ratios before washing are 94 - 95 : 6 - 4.
15A process as. claimed in claims 1 - 14 wherein the isomers 1 & 2 ratios after solvent wash is 96 - 97 : 4 -3.
16. A process as claimed active isomer
in claims 1-15, wherein the purity of insecticidally commonly known as lambda cyhalothrin obtained is 95 %
minimum.







ABSTRACT
1. A process for the preparation of Lambda cyhalothrin of formula I

Formula I
which is useful as an insecticide with contact and stomach action and repellant properties and is used to control a wide variety of insect pests like aphids, thrips, Lepidoptera larvae, Coleoptera larvae and adults, comprises the epimerization of cis - cyhalothrin in presence of organic amines and co bases and seeding the reaction mixture with small quantities of very pure Lambda cyhalothrin at sub zero temperatures to give the insecticidally active isomer namely the ester derived from (+) cis acid and a - (S) - alcohol [ISOMER 1] commonly known as Lambda cyhalothrin of very high purity..