Synthetic Pyrethroids

4 Recent Progress in Syntheses of the N e w and Most

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Potent Pyrethroids NOBUSHIGE ITAYA, TAKASHI MATSUO, NOBUO OHNO, TOSHIO MIZUTANI, FUMIO FUJITA, and HIROSUKE YOSHIOKA Synthesis Laboratory, Pesticide Division, Institute for Biological Science, Sumitomo Chemical Co. Ltd., 4-2-1 Takatsukasa, Takarazuka, Hyogo 665, Japan

There have been disclosed a number of potent and photostable pyrethroids in which 3-phenoxybenzyl group or i t s α-cyano derivative are incorporated as alcohol moieties "Figure 1". 3-Phenoxybenzyl alcohol and i t s α-cyano derivative had originally been discovered to be useful as esters of chrysanthemic acid, i . e . S-2539 or Phenothrin (1,2), and S-2703 (3,4), the potent pyrethroids. Moreover, the former pyrethroid has been known to be more resistant to photo-irradiation than the pyrethroids with other alcohol moieties such as 5-benzyl-3-furylmethyl alcohol (5). But, the photo-stabilities of these pyrethroids had been assessed to be still insufficient under agricultural f i e l d conditions On the other hand, the acid moieties recently developed, i . e . 2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropanecarboxylic acid (6,7) and α - ( 4 - c h l o r o p h e n y l ) - i s o v a l e r i c acid (8,9) have the double bonds stabilized by the two electron-withdrawing chlorine atoms or by the aromatization forming the chloro-substituted benzene ring. 2,2,3,3-Tetramethylcyclopropanecarboxylic acid has apparently no double bond. Therefore, the esters of these acids are much more stable to photo-irradiation than the esters of chrysanthemic acid. Among these new pyrethroids, S-3206 or Fenpropanate (3,4), NRDC-143 or Permethrin (10), NRDC-149 or Cypermethrin (11) and S-5602 or Fenvalerate (8,9) are being assessed to be most promising insecticides for agricultural use owing to their extraordinarily high potency and sufficient f i e l d persistency. Meanwhile, there have been a variety of synthesis studies seeking for the best chemical processes for production of the respective new pyrethroids. In this connection, we now briefly review a number of known synthetic pathways and report new routes leading to the important synthetic pyrethroids and some of their essential intermediates. Method of

esterification

Figure 2 f i r s t represents a conventional method to prepare 45

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

SYNTHETIC PYRETHROIDS

46

CHR ι

C Ν

R.

S-2703

S-2539

1


OR PHENOTHRIN

S-3206 OR FENPROPANATE

NRDC-143

NRDC-W9

OR PERMETHRIN

OR C Y P E R M E T H R I N

α S-5602 OR

Figure 1.

oy

FENVALERATE

Potent synthetic pyrethroids

ο (-CH ) 3

OoiX T.MIZUTANI JAP.

Figure 2.

ET A L .

PAT.11106

Bf

(1976)

Intermediates of 3-phenoxybenzyl esters


4.

ITAYA E T A L .

Most Potent

Pyrethroids

47


3-phenoxybenzyl a l c o h o l , which i s an i n t e r m e d i a t e o f P h e n o t h r i n a n d P e r m e t h r i n , a n d i n t r o d u c e s i n c o n t r a s t a new m e t h o d o f t h e p r e p a r a t i o n o f 3 - p h e n o x y b e n z y l e s t e r s w i t h a new i n t e r m e d i a t e . So f a r , b o t h t h e a c i d a n d t h e a l c o h o l a r e p r i m a r i l y t h e r e q u i s i t e s f o r t h e p r e p a r a t i o n o f t h e s y n t h e t i c p y r e t h r o i d s . The c o n v e n t i o n a l method t o p r e p a r e t h e 3-phenoxybenzyl e s t e r c o m p r i s e s the o x i d a t i o n o f 3-phenoxytoluene by a u t o - o x i d a t i o n a t t h e methyl group t o form 3-phenoxybenzoic a c i d , t h e c o n v e r s i o n o f t h e a c i d i n t o the methyl e s t e r and t h e r e d u c t i o n o f the e s t e r w i t h a c o s t l y h y d r i d e r e a g e n t t o y i e l d t h e o b j e c t i v e a l c o h o l , w h i c h i s t o be e s t e r i f i e d with the optional a c i d chloride to give the f i n a l pyrethroid ester. On t h e o t h e r h a n d , t h e new r o u t e c o m p r i s e s two c h a r a c t e r i s t i c s t e p s . The f i r s t s t e p i s t h e p r e p a r a t i o n o f t h e q u a r t e r n a r y ammonium s a l t , 3 - p h e n o x y b e n z y l t r i e t h y l ammonium b r o m i d e ( 1 2 ) , a n d t h e s e c o n d s t e p i s t h e c o n d e n s a t i o n o f t h e ammonium s a l t w i t h t h e s o d i u m s a l t o f t h e o p t i o n a l a c i d (13). The p r e p a r a t i o n o f t h e ammonium s a l t i s a c h i e v e d b y t h e b r o m i n a t i o n o f 3-phenbxytoluene a t t h e methyl group f o l l o w e d by the q u a r t e r n i z a t i o n w i t h t r i e t h y l a m i n e . We i n i t i a l l y i n t e n d e d t o p r e p a r e p u r e 3 - p h e n o x y b e n z y l b r o m i d e , w h i c h i s t o be c o n v e r t e d i n t o t h e o b j e c t i v e e s t e r w i t h t h e s o d i u m s a l t o f t h e o p t i o n a l a c i d , b u t we e n c o u n t e r e d two m a j o r d i f f i c u l t i e s i n t h i s a t t e m p t . One o f w h i c h was t h a t t h e s e l e c t i v i t y f o r t h e b e n z y l b r o m i d e was n o t h i g h e n o u g h t o n e g l e c t t h e f o r m a t i o n o f t h e b e n z a l b r o m i d e a n d a number o f b y - p r o d u c t s b r o m i n a t e d a t t h e a r o m a t i c n u c l e i . The a n o t h e r d i f f i c u l t y was l a c k of heat s t a b i l i t y o f the bromination mixture, t h a t i s e s s e n t i a l f o r t h e r e c t i f i c a t i o n t o i s o l a t e t h e b e n z y l bromide from t h e mixture. T h e s e d i f f i c u l t i e s were s u c c e s s f u l l y o v e r c o m e b y t h e q u a r t e r n i z a t i o n p r o c e d u r e . T h u s , t h e r e s u l t i n g ammonium s a l t c a n be i s o l a t e d i n a pure s t a t e a s e i t h e r c r y s t a l s by f i l t r a t i o n o r an aqueous s o l u t i o n l e a v i n g o t h e r w a t e r - i n s o l u b l e m a t e r i a l s i n a n o r g a n i c l a y e r on phase s e p a r a t i o n , and t h e y i e l d i s q u a n t i t a t i v e on t h e b a s i s o f t h e b e n z y l b r o m i d e c o n t e n t . In order t o i n i t i a t e the e s t e r i f i c a t i o n r e a c t i o n , a mixture o f t h e a q u e o u s ammonium s a l t a n d t h e s o d i u m s a l t o f t h e o p t i o n a l a c i d i s b o i l e d i n a proper organic solvent t o a z e o t r o p i c a l l y remove w a t e r . T r i e t h y l a m i n e i s r e l e a s e d i n s e q u e n c e o f t h e e s t e r i f i c a t i o n a n d a few p e r c e n t o f N , N - d i e t h y l - 3 - p h e n o x y b e n z y l a m i n e and t h e e t h y l e s t e r o f t h e a d o p t e d a c i d a r e d e t e c t e d i n t h e c r u d e p r o d u c t , w h i c h a p p a r e n t l y r e s u l t f r o m t h e N-C b o n d c l e a v a g e o f N - e t h y l b o n d i n s t e a d o f t h e N - b e n z y l b o n d c l e a v a g e " F i g u r e 3". The t e r t i a r y amine c a n be removed b y a c i d - w a s h i n g a n d t h e e t h y l e s t e r c a n be d i s t i l l e d o f f u n d e r r e d u c e d p r e s s u r e . The y i e l d o f the f i n a l b e n z y l e s t e r i s o v e r 90% a n d t h e p u r i t y o f t h e b e n z y l e s t e r i s o v e r 90%. T h i s new m e t h o d i s more p r a c t i c a l t h a n t h e c o n v e n t i o n a l method, because t h e u s e o f a c o s t l y and dangerous h y d r i d e



CH2R MAIN

Acid Na NEt

PRODUCTS

NEt

3

NaBr

3

MINOR

0-o-^^NEt

2


BY-PRODUCT!

Acid ethyl ester CK

or

Figure 3.

New method to prepare 3-phenoxybenzyl esters

NaOH ptc N.OHNO ET PTC = PHASE TRANSFER

Figure 4.

FARKAS METHOD

CATALIST

AL.

UNPUBLISHED

(1971)

Syntheses of acid moieties (S-3206 and S-5602)

CI C l / ^ =
^ ^Μ^^Λ

Γ

Η+

+ o t h

e s) r

(νΠ)Τγ. 40X

(VDCCI3

MeOH £ > ^ > ( ^ e NaOMe ^ > = X c 0 M e 2

H C l

( v n n

Cl

DV acid ester Y.

90X FROM ( V U )

CIS/TRANS -

Figure 7.

3/7

N.ITAYA ET

AL.

UNPUBLISHED(1976)

New method to prepare the DV acid (from 1,1,1-trichloro-2-hydroxy-4-methyl-3- or -4-pentene)

Figure 8.

Assumed mechanism of the lactone formation


SYNTHETIC

PYRETHROIDS

A,

COoEt EtOH EtO>_. ^ ^ O H ^F^O ^ T ^ E t -EtOH

(IX)

XP2B

(X)


(XII)

or

>1

"MgQ (ΧΠ)

(ΧΠΙ) Figure 9.

Helvetica Chimica Acta

Methods to prepare 4,4-dimethyl-5-hexen-2-one. first method was presented by Brack et al (22).

0(Χ

^ Λ Χ Λ

(ΧΠ)

C

C

l

3

c

l

ΛΧλ

N§OH (XIV)

C

The

C

l

33 l

(XV) (XV

Y.

Y. 797.

CIS/TRANS =

\b -

C2H5-C

o c H

3 a h.

5

W _/gc

ocV'

9/1

QUANT.

N i

Me Me

'"

(XV)

(XIV)

Modern Synthetic Reactions

Figure

10.

0

Formation of cis-cyclopropylmethyl and assumed mechanism (24)

u^ca

3

ketone

cis DV acid

(XVI)

Y. 85% CIS/TRANS =

9/1

CIS/TRANS =

9/1

v4& MATSUO ET A L .

(χνπ)

UNPUBLISHED

Y

F.FUJITA

trans DV acid ;,S/TRANS =

1/9

UNPUBLISHED

(i976)

Y. 877. CIS/TRANS =

Figure 11.

(1975)

ET A L .

1/9

Formation of cis- and trans-DV acid from cis-cyclopropylmethyl ketone


4.

ITAYA E T A L .

Most Potent

53

Pyrethroids

t o e i t h e r o f t h e c i s o r t h e t r a n s D V - a c i d may be c o n d u c t e d in o n e p o t r e a c t i o n . And, i f t h e DV-acid o f an o p t i o n a l c i s / t r a n s r a t i o i s p r e f e r r e d , i t may be done b y a p r o p e r s e l e c t i o n o f t h e r e a c t i o n c o n d i t i o n s in t h e c y c l o p r o p a n e r i n g c l o s u r e a n d t h e s u b s e q u e n t s t e p s . T h e p r e s e n t method h a s a n u n i q u e a d v a n t a g e o v e r t h e o t h e r methods, s i n c e t h e p y r e t h r o i d s d e r i v e d from t h e D V - a c i d have d i f f e r e n t i n s e c t i c i d a l n a t u r e s , d e p e n d i n g o n t h e c i s / t r a n s isomer r a t i o s .


T a b l e I.

RELATIVE TOXICITIES OF CIS AND TRANS ISOMERS HOUSEFLY

COMPD.

ISOMER

(TOPICAL APPLICATION) LD (Y/FLY) 5 0

GERMAN COCKROACH (FILM COTACT METHOD) LC

2

5 0

(MG/M )

CIS

0.012

(1.7)

0.88

(1.9)

TRANS

0.020

(1.0)

1.7

(1.0)

CIS

0.0032

(1.9)

0.16

(2.2)

TRANS

0.0060

(1.0)

0.35

(1.0)

HRDC-M3

NRDC-119

Table I represents ther e l a t i v e i n s e c t i c i d a l potencies o f t h e c i s a n d t r a n s NRDC-143 a n d -149, in w h i c h t h e c i s i s o m e r s a r e n e a r l y t w i c e more t o x i c t o i n s e c t s t h a n t h e c o r r e s p o n d i n g trans i s o m e r s , T h e r e f o r e , t h e c i s p y r e t h r o i d s a r e more p r e f e r r e d t h a n the t r a n s p y r e t h r o i d s from t h e potency c r i t e r i a and t h i s i s t h e f i r s t r e p o r t o f t h e s e l e c t i v e method f o r t h e c i s d o m i n a n t D V - a c i d .

Literature Cited 1.

2.

3. 4.

Itaya,Nobushige; Kitamura,Shigeyoshi; Kamoshita,Katsuzo; Mizutani,Toshio; Nakai,Shinji; Kameda,Nobuyuki; Fujimoto, Keimei; Okuno,Yoshitoshi; Japan. 71 6,904 Fujimoto,Keimei; Okuno,Yoshitoshi; Itaya,Nobushige; Kamoshita,Katsuzo; Mizutani,Toshio; Kitamura,Shigeyoshi; Nakai,Shinji; Kameda,Nobuyuki; Japan. 71 21,473 Matsuo,Takashi; Itaya,Nobushige; Okuno,Yoshitoshi; Mizutani, Toshio; Ohno,Nobuo; Kitamura,Shigeyoshi; Japan. 76 5,450 Matsuo,Takashi; Itaya,Nobushige; Mizutani,Toshio; Ohno,Nobuo; Fujimoto,Keimei; Okuno,Yoshitoshi; Yoshioka,Hirosuke; Agr.Biol.Chem.(1976) 40, 247.


54 5. 6. 7.


8.

9.

10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.


Fujimoto,Keimei; Itaya,Nobushige; Okuno,Yoshitoshi; Kadota, Tadaomi; Yamaguchi,Takashi; Agr.Biol.Chem.(1973) 37, 2681. Elliott,Michael; Farnham,Andrew W.; Janes,Norman F . ; Needham, Paul H . ; Pulman,David Α . ; Nature,Lond.(1973) 244, 456. Farkaš,Jiří; Kouřím,Pavel; Šorm,František; Chem.listy(1958) 52, 688. Fujimoto,Keimei; Ohno,Nobuo; Okuno,Yoshitoshi; Mizutani, Toshio; Ohno,Isao; Hirano,Masachika; Itaya,Nobushige; Matsuo, Takashi; Japan.Kokai 74 26,425 Ohno,Nobuo; Fujimoto,Keimei; Okuno,Yoshitoshi; Mizutani, Toshio; Hirano,Masachika; Itaya,Nobushige; Honda,Toshiko; Yoshioka,Hirosuke; Agr.Biol.Chem. (1974) 38, 881. Elliott,Michael; Farnham,Andrew W.; Janes,Norman F . ; Needham, Paul H . ; Pulman,David Α . ; Nature,Lond.(1973) 246, 169. Elliott,Michael; Farnham,Andrew W.; Janes,Norman F . ; Needham, Paul H . ; Pulman,David Α . ; Pestic.Sci. (1975) 6, 537. Mizutani,Toshio; Ume,Yoshitaka; Matsuo,Takashi; Japan. 76 11,106 Mizutani,Toshio; Ume,Yoshitaka; Matsuo,Takashi; Japan.Kokai 75 46,648 Matsui,Masanao; Kitahara,Takeshi; Agr.Biol.Chem. (1967) 31, 1143. Ohno,Nobuo; Umemura,Takeaki; Watanabe,Tetsuhiko; Japan.Kokai 76 63,145 Kondo,Kiyoshi; Matsui,Kiyohide; Negishi,Akira; Takahatake, Yuriko; Japan.Kokai 76 65,734 Mori,Fumio; Ohmura,Yoshiaki; Nishida,Takashi; Itoi,Kazuo; Japan.Kokai 76 41,324 Itaya,Nobushige; Matsuo,Takashi; Magara,Osamu; (unpublished) Payne,George B . ; J.Org.Chem. (1967) 32, 3351. Itaya,Nobushige; Fujita,Fumio; (unpublished) Colonge,Jean; Perrot,André; Bull.Soc.Chim.France. 1957, 204. Brack,K.; Schinz,H.; Helv.Chim.Acta. (1951) 34, 2005. Von Fraunberg,Karl; Ger.Offen. 2,432,232. House,Herbert O.; "Modern Synthetic Reactions. 2nd Edition" W.A.Benjamin,Inc. Menlo Park,California 1972 Matsuo,Takashi; Itaya,Nobushige; Magara,Osamu; (unpublished) Fujita,Fumio; Itaya,Nobushige; Matsuo,Takashi; (unpublished)


Synthetic Pyrethroids

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