Synthetic Pyrethroids

3 Pyrethroid Insecticides Derived from Some Spiroalkane Cyclopropanecarboxylic Acids R. H . DAVIS and R. J. G. SEARLE

Downloaded by COLUMBIA UNIV on September 14, 2017 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0042.ch003

Shell Research Ltd., Shell Biosciences Laboratory, Sittingbourne Research Centre, Sittingbourne, Kent ME9 8AG, England

The h i s t o r i c a l development of s y n t h e t i c p y r e t h r o i d s falls roughly i n t o three stages. Initially there was a concentration on the s t r u c t u r a l e l u c i d a t i o n of the n a t u r a l p y r e t h r i n s , t h i s was followed by a search f o r simpler a l c o h o l components from which to form e s t e r s with the n a t u r a l acids and in the l a s t decade considerable a t t e n t i o n has been devoted to expanding the v a r i e t y of acids that can give p y r e t h r o i d esters of s i g n i f i c a n t i n s e c t i c i d a l a c t i v i t y on a broad spectrum of s p e c i e s . The success of t h i s l a t t e r work i s demonstrated by the s e l e c t i o n of a c i d s t r u c t u r e s shown (Figure 1).

The structure-activity relationships derived from the work on acid components may be briefly summarised as follows:(a)

The cyclopropane ring i s not essential for activity (1 ).

(b)

Trisubstitutedcyclopropane acids bearing unsaturated substituents give high a c t i v i t y ; several such substituents are known and geometrical configuration can be important (2).

(c)

In unsymmetrical acids activity is highly dependent on chirality (_3, 4_) . (The only exception i s 2,2-dimethylcyclopropanecarboxylic acid (5).)

(d)

Geminal dimethyl groups are an essential structural requirement (3).

(e)

Few tetrasubstitutedcyclopropanecarboxylic acids give active esters (6).

37

Elliott; Synthetic Pyrethroids ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SYNTHETIC PYRETHROIDS

38

Although search

many

for

agricultural suitable

of

these

stable

observations

pyrethroids

pests

was

started,

some

scope of

for

the

new

synthesis.

allethronyl

it

and

although

use,

it

groups


was of

such

soon

this

these

rings

in

the

well-known used

were

the

many

of

in

with

the

the

with

In second

and

interestingly, the

the

gives

1

:

Ring offers

a

a

A

in

of

to

give

to

(11).

by

by

of

a

9^,

alkane

10),

one

as

of

was

ready

In

those

also

(Figure

the

an

type the

the

is

4)

1,2

migration evidence

readily

mono,

cyclopropanecarboxylic

that

contracts acid. d i ,

acids

of

and

is

with

in

which

In

this, a

f

the i t

the

- C

base

the

use

well-

has

been

semibenzilic

hydroxide

concerted C

which

of

avoids to

(13)

of

only

contrast

aqueous

method

similar

adds

to

displacement

of

carbonyl

unsymmetrical

ion

bond

mechanism

is

2-bromo-2,3,3,4,4-pentamethylto

the

corresponding

The

scope

of

t r i ,

tetra

and

to

methyleneand,

(12).

useful

by an

was

produces

This

acids

the

for

which

uses

products

mechanism

followed

the

cyclopropane-

materials

ot-haloketones

operative.

atom

observation

allows

of

unsymmetrical

where

ketene-olefin

methylenecyclopropane

superficially

rearrangement

possible

contraction

cases

cycloaddition

possible

interesting

ring

the

cyclobutanones. to

was

two

other

to

three the

diazoacetate

olefin the

a

starting

by 2)

ethyl

cyclobutanone

sequence

case

Although

cyclopropanecarboxylic thus

(cf.

same

contraction

dimethyIketene

Further

cyclobutanone

view

dimethyl

(Figure

available,

prepare

ring

isomeric

carbon

5).

benzyl

In

spirofused

with

the

only

readily

typical

this

3)

underwent

base

to

olefin

cyclopropanecarboxylic

that

ion

(6)

agronomic

achieved

α-halocyclobutanones

(11)

method

an

was

these

of

Favorski

afforded

of

of

contraction

carbonyl

described

geminal

by

a c t i -

2,2,3,3-

for

acids

materials first

(Figure

not

mechanistically

shown

(Figure

acid

unreported

dimethyIketene

diazoester.

halide

the

of

afforded

substituted

both

known

the

replacing

our

dearth

photostable.

of

rearrangement

of

been

several and

the

insecticidal

unstable

1 mixture

preparation of

of

which

used

prior

possible

addition a

was

were

acid.

cyclobutane

that

the

when

control

acids

esters had

too

active

the

aqueous

olefin

halogenated

carboxylic

acid

be

8)

required

chloroketene

cycloadditions

to

Ç7, both

cyclopropanation

treated

of

would

previously

methods.

and

appropriate

one

that

Previously

effect

α-chlorocyclobutanones

then

appeared

to

studied.

Synthesis

when

used

tetramethylcyclopropane

give

interrelated

reacted

evident

results,

to

esters

acid

systematically

was

available

be

pyrethronyl

tetramethylcyclopropanecarboxylic and,

of

not

could

tetrasubstitutedcyclopropanecarboxylic

vity

esters

were

that

be

the

ring

pentamethylcontraction

pentasubstituted-

prepared.


3.

DAVIS A N D SEARLE

Derived

Pyrethroid

Insecticides

39

R - H : R = C K , C H C H , CH « C H 3

3

2

2

#

R - R = CH, COOH

R = C H : R = COOCH3 3


R = R - F, CI, Br

H C\ /CH 3

0

H C

CH

3

3

3

γ

CHCOOH

H C 3

-COOH H C 3

Figure 1.

Some acids which give active pyrethroid esters

H C 3

y=< H C^

Ph P 3

H„C

3

+ \

Ph P0 3

|

NLCHCOOEt

NaOH H C

H C

3

3

-COOH

-COOEt

H C

H C

3

3

Figure 2.

Synthesis from diazoester-olefin addition

COOH Figure 3.

Synthesis from chloroketene-olefin cycloaddition


40

SYNTHETIC

PYRETHROIDS

CH, H C3

H C 3


Br,

CH., H C3

COOH

Figure 4.

aq-ICjCOs

Synthesis from dimethylketene-olefin

cycloaddition

General mechanism

Ο

II

C—Β a Hal

12Hal

Specific example H C 3

H C-

aq. KjCOg

3

-Br

H C3

H C 3

CHFigure 5.

Ring contraction of a-halocyclobutanones



T.u. = Tetranychus urticae

VII

VI

3

3

CH

IV

\

D> D>

=1/

55

Resmethrin

230

8.9

6.8

5.?

9 0

K» min

2.1

2.8

5.7

5.2

9.5

6.4

0.4

4.8

0.1

3.8

0.05

0.025

% Concentration

5 0

KD min

Knockdown activity

cyclopropanecarboxylates

245 4

620

1

15

24

1

Synthetic Pyrethroids

Recommend Documents