Cyanoalkyl Phosphorodithioates - American Chemical Society

Chapter 19 Synthesis, Insecticidal Activity, and Field Performance of Some S-Cyanoalkyl Phosphorodithioates 1

1

1

J. R. Sanborn ,R. L. Sagaser, D. Marsden , T. A. Andrea , and Β. T. Grayson

Downloaded by UNIV LAVAL on May 9, 2016 | http://pubs.acs.org Publication Date: November 3, 1987 | doi: 10.1021/bk-1987-0355.ch019

2

Biological Sciences Research Center, Shell Agricultural Chemical Company, P.O. Box 4248, Modesto, CA 95352

This report summarizes the synthesis, insecticidal activity, and field performances of some S-cyanoalkyl phosphorodithioates related to terbufos. Replacement of one of the methyl groups of terbufos with a nitrile yielded an insecticide more active than terbufos but lacking its soil persistence. However, addi tion of a methyl group to the carbon between the two sulfur atoms of this S-cyanoalkyl phosphorodithioate produced a com pound that was almost as active as Terbufos as an insecticide and gave economic control of corn rootworms at 1 1b/A. The i n c o r p o r a t i o n o f a as shown below:

C H -HN^^N 2

5

Î Î Î

nitrile

^NH-iC3H7

Atrazine

group i n t o a t r a z i n e y i e l d e d B l a d e x

X

C H -HN ^N^^NH-C(CH3) CN 2

5

2

^

Bladex

an h e r b i c i d e w i t h s l i g h t l y d i f f e r e n t p h y s i c a l and b i o l o g i c a l characteristics. Perhaps t h e most s i g n i f i c a n t change i n t h e molecule i s i t s decreased s o i l p e r s i s t e n c e , which i s r e l a t e d t o t h e a b i l i t y o f t h e n i t r i l e m o i e t y t o undergo h y d r o l y s i s and a f f o r d s i g n i f i c a n t l y less h e r b i c i d a l products.

1Current address: Ε. I. du Pont de Nemours & Co., Wilmington, DE 19898 Current address: Shell Biosciences Laboratory, Sittingbourne, England

2

0097-6156/87/0355-0209$06.00/0 © 1987 American Chemical Society

Baker et al.; Synthesis and Chemistry of Agrochemicals ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

SYNTHESIS AND CHEMISTRY OF AGROCHEMICALS

210

This feature allows the farmer to plant other t r i a z i n e susceptible crops i f h i s f i r s t crop i s l o s t because of environmental f a c t o r s . Other physical properties that are changed because of the presence of the cyano group are a nearly 5-fold increase i n water s o l u b i l i t y (Atrazine=33ppm, Bladex 160 ppm) and an approximate 200-fold decrease i n the vapor pressure (Atrazine=3.0xl0 mm,Bladex l.6x10 mm) · Since a n i t r i l e group addition to the t r i a z i n e herbicide Atrazine did not s i g n i f i c a n t l y detract from i t s f i e l d performance, we decided to examine what effect a n i t r i l e group might have on the i n s e c t i c i d a l and f i e l d performance of the highly successful corn rootworm i n s e c t i c i d e Q . , 2 ) , terbufos, whose structure i s shown below: e


e

u (C2H 0)2P-SCH SC(CH3)3 5

2

i +

CN

«·-

j

(C HsO)2-P-S-CH -S-C-CN CH 2

2

3

The following questions come to mind as to what might happen to the physical properties and i n s e c t i c i d a l a c t i v i t y of terbufos i f a n i t r i l e group was incorporated into i t : 1. Is the vapor pressure reduced? 2. W i l l the s o i l persistence be less and therefore the f i e l d e f f i c a c y be reduced? 3. W i l l the insect spectra be changed compared to terbufos which only controls corn rootworms? 4. How w i l l the incorporation of a n i t r i l e affect the economics of the manufacture of the compound compared to other c o r n - s o i l insecticides? Patent Background Since, organophosphorus i n s e c t i c i d e s have been a r t i c l e s of commerce f o r about 35-40 years, i t was necessary to c a r e f u l l y examine the patent l i t e r a t u r e to determine i f there was p r i o r art germane to this work. There were two related patents i n t h i s area (3,4) and they are associated with the structures shown below. S

CH X

II

2

I

(C2H 0) PS(CH2)nS-Ç-CN 5

2

CH X=halogen, n=l X=H, n=2

3

Ref. 3 Ref. 4

Synthetic Route In order to prepare the desired product, the intermediate i n below was required. ÇH X 2

CH SC-CN I CH 3

3

X=H or halogen


19.

SANBORN ET AL.

211

S-Cyanoalkyl Phosphorodithioates

For t h e s e i n t e r m e d i a t e s , t h e t h r e e r o u t e s d e p i c t e d below were u t i l i z e d f o r t h e p r e p a r a t i o n o f both t h e n o v e l compounds as w e l l as those r e q u i r e d f o r t h e p r i o r a r t examples. 1.

CH SNa 3

(CH ) (CN)CX

+

3

»

2

(CH ) (CN)C-SCH 3

2

3

X «= BrORMesyl

2.

(CH ) CHCN ^ ^ S S C T ^

3.

H2OCCH3CN +

3

W*hC(CH)SCH

2

3

CH O Downloaded by UNIV LAVAL on May 9, 2016 | http://pubs.acs.org Publication Date: November 3, 1987 | doi: 10.1021/bk-1987-0355.ch019

2

3

•

3

3

ί* CIH2S-Ç-CN

2

CH SQ

SCH3 For t h e f i r s t r e a c t i o n scheme, t h e bromo n i t r i l e was p r e p a r e d v i a r a d i c a l b r o m i n a t i o n o f t h e a p p r o p r i a t e n i t r i l e , and t h e m e s i t y l e s t e r was p r e p a r e d b y t r e a t m e n t o f a c e t o n e c y a n o h y d r i n . W i t h m e s i t y l c h l o r i d e i n t h e presence o f an amine base. The next two r o u t e s a r e s u f f i c i e n t l y c l e a r t o r e q u i r e no f u r t h e r e x p l a n a t i o n . F i n a l s y n t h e s i s o f t h e d e s i r e d p r o d u c t i s shown v i a t h e two e q u a t i o n r e a c t i o n sequence shown below. CH C1 2

CH SC(CH ) 3

3

+ S0 C1

2

2

2

2

or NCS

•

C1CH SC(CH ) CN 2

3

2

I

s 11

I

+ (C H 0) -P-SNa 2

5

2

s THF ™* >

" (C H 0) -P-SCH SC(CH ) CN 2

5

2

2

3

2

P r i m a r y I n s e c t i c i d e S c r e e n i n g Data The l a b o r a t o r y t e s t i n g o f t h e s e m o l e c u l e s was c a r r i e d o u t on f o u r i n s e c t s , t h e h o u s e f l y , Musca d o m e s t i c a , M.d., t h e pea a p h i d , A c r y t h o s i p h o n pisum, A.P., t h e c o r n earworm, H e l i o t h i s z e a , H.z., and t h e t w o - s p o t t e d s p i d e r m i t e , T r i t i c u m u r t i c a e , T.u. In a l l t o x i c i t y t e s t e v a l u a t i o n s , p a r a t h i o n was employed as a s t a n d a r d . T h e r e f o r e , any compound h a v i n g a T o x i c i t y Index ( T I ) o f 100 i s e q u a l t o p a r a t h i o n . The d a t a f o r t h e l a b o r a t o r y t o x i c i t y e v a l u a t i o n o f these m o l e c u l e s a r e c o l l e c t e d i n T a b l e s 1 and 2. E x a m i n a t i o n o f t h e d a t a shows t h a t t h e f i r s t e n t r y i n t h e T a b l e 1 h a d e x c e p t i o n a l l y h i g h a c t i v i t y on a p h i d s a n d m i t e s w i t h T I v a l u e s o f 1750 and 3192, r e s p e c t i v e l y . F o r h o u s e f l i e s and c o r n earworms t h i s compound was l e s s a c t i v e than t h e s t a n d a r d p a r a t h i o n . I n c r e a s e s i n s i z e o f t h e s u b s t i t u e n t R s i g n i f i c a n t l y reduced t h e a c t i v i t y a g a i n s t a l l i n s e c t s except t h e c o r n earworm where a major r e d u c t i o n o n l y o c c u r r e d when t h e hydrogen was r e p l a c e d by e t h y l and l a r g e r groups. The m o l e c u l e s i n T a b l e 2 shown below have a s u b s t i t u e n t b e t a t o the n i t r i l e group. F o r comparison, two o f t h e m o l e c u l e s from T a b l e 1 have been i n c l u d e d .


212


T a b l e 1.

I n s e c t i c i d e E v a l u a t i o n o f some Phosphorodithioates

S^cyanoalkyl

S II (C H 0)2-P-SCH-SC(CH )2CN ι R 5

2

T o x i c i t y Index ( p a r a t h i o n = 100) M.d. A.p. H.z. T.u.

R


3

H CH c i n C^H £

?

S C H

3 terbufos

T a b l e 2·

56 13 8 4 2 19

1750 66 56 46 103 85

3192 496 438 120 68 617

16 16 5 + 0 14

I n s e c t i c i d e E v a l u a t i o n o f some Phosphorodithioates

S-cyanoalkyl

S II (C H 0) -P-SCHSC(CH ) (CN) CH Y ι X T o x i c i t y Index ( p a r a t h i o n = 100) M.d. A.p. H.z. 2

H Η H Cl Η CH. Cl CH^ απ C Η Η SCH^ terbufos

5

56 19 13 3 12 15 19

2

3

1750 60 66 28 32 309 85

2

16 3 16 4 6 + 14

T.u. 3192 3341 496 112 106 267 617


19.

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213

I n g e n e r a l compounds p o s s e s s i n g a s u b s t i t u e n t ( C l , ^ H ^ , SCH^) beta to the n i t r i l e s u b s t i t u e n t are l e s s a c t i v e a g a i n s t these i n s e c t s than compounds w i t h o n l y hydrogens i n t h i s p o s i t i o n . The o n l y e x c e p t i o n i s f o r the f i r s t two e n t r i e s i n T a b l e 2 where the c h l o r i n a t e d d e r i v a t i v e appears t o be somewhat more a c t i v e on m i t e s than i t s u n c h l o r i n a t e d analogue.


Laboratory D i a b r o t i c a j a r t e s t S i n c e these m o l e c u l e s were i n i t i a l l y prepared t o be used as a s o i l i n s e c t i c i d e , i t was n e c e s s a r y t o e v a l u a t e them i n a l a b o r a t o r y b i o assay t o determine i f any of them had s u f f i c i e n t a c t i v i t y t o m e r i t a f i e l d e v a l u a t i o n as a s o i l i n s e c t i c i d e f o r c o n t r o l of i n s e c t s i n j u r i o u s t o f i e l d c o r n i n the Midwest. The p r o t o c o l t o e v a l u a t e p o t e n t i a l s o i l i n s e c t i c i d e s f o l l o w s t h a t d e s c r i b e d previously^)· B r i e f l y , i t c o n s i s t s of a 4 o z . j a r c o n t a i n i n g 20 g of i n s e c t i c i d e t r e a t e d s o i l c o n t a i n i n g two cornseeds moistened by damp v e r m i c u lite. I n t o t h i s j a r are p l a c e d 20 eggs of the Southern c o r n r o o t worm, D i a b r o t i c a undecimpunctata h o w a r d i . A f t e r about 10 days the j a r c o n t e n t s are examined f o r the presence of l i v e l a r v a e . A secondary assessment of f e e d i n g damage by the hatched l a r v a e t o the r o o t s of the germinated c o r n s e e d l i n g s i s a l s o made. I n o r d e r t o q u a n t i t a t e the r e s u l t s , comparisons a r e made w i t h number of l i v e l a r v a e i n the u n t r e a t e d c o n t r o l . For example, i f the number of l a r v a e i n a t r e a t e d j a r i s e q u a l t o the number i n the u n t r e a t e d c o n t r o l than a s c o r e of 4 i s g i v e n . I f a t r e a t e d j a r has no l i v e l a r v a e then a s c o r e of 0 i s g i v e n . N u m e r i c a l v a l u e s t h e r e f o r e , of 1-3 are g i v e n f o r t r e a t e d j a r s t h a t have l i v e l a r v a e i n them t h a t are l e s s than the u n t r e a t e d check but g r e a t e r t h a n z e r o . To d e t e r mine t h e p e r s i s t e n c e o f a new compound, t h e s o i l i s aged f o r p e r i o d s o f time up t o 8 weeks. S i n c e t e r b u f o s i s u t i l i z e d b r o a d l y i n the Midwest t o c o n t r o l D i a b r o t i c a s p e c i e s a s s o c i a t e d w i t h c o r n , i t s e r v e d as the s t a n d a r d i n the l a b o r a t o r y a s s a y . T a b l e 3 g i v e s d a t a f o r the performance o f t e r b u f o s i n the l a b o r a t o r y b i o a s s a y at 1.0 and 0.3 ppm.

Table 3 .

Performance of T e r b u f o s i n a L a b o r a t o r y D i a b r o t i c a J a r Test

Concentration (ppm) 1.0 0.3

0 0 0

Time (weeks) 4 2 0 0 0 0

8 0 1

Only a t the end of the e i g h t h week are t h e r e a few l i v e l a r v a e as i n d i c a t e d by a n u m e r i c a l v a l u e of 1. I n T a b l e 4 below are d a t a f o r e v a l u a t i o n of the t h r e e b e s t compounds i n the D i a b r o t i c a j a r t e s t .


214


Table 4.

Performance o f Three j v - C y a n o a l k y l P h o s p h o r o d i t h i o a t e s i n a Laboratory J a r Test S u (C H 0)2-P-SCHSC(CH3) (CN) CH Y ι X 2


Concentration P.P.M.

5

2

Time (weeks) 2 4

0

Structure X Y

8_

1.0 0.3

0 -

4

H

1.0 0.3

0 0

0 0

0 1

0 4

CH

1.0 0.3

0 2

0 3

0 3

0 3

CH

H

3

H

Cl

Examination of these data c l e a r l y shows that none of the three compounds i s as e f f e c t i v e as terbufos i n the j a r t e s t . Perhaps the most interesting aspect of this data i s the r e l a t i v e s o i l e f f i c a c y of the second compound compared to the f i r s t . The substitution of a methyl group for a hydrogen between the two sulfur atoms greatly enhances the s o i l a c t i v i t y of this molecule. Quantitation of the r e l a t i v e s o i l s t a b i l i t y of these three molecules as measured by the bioassay data are collected i n Table 5 using a pseudo f i r s t order k i n e t i c analysis of the data. Table 5 .

Estimated S o i l Persistence of Three j5-Cyanoalkyl Phosphorodithioates S Ν (C H 0) -P-SCH-SC (CH ) X 2

5

2

3

2

R Structure

S o i l Half L i f e

R

Χ

T

Η Η CH. c l

CH. CN CN CN

>35 5 10 20

2

5

l/2

(

d

a

v

s

)

Clearly terbufos, the f i r s t entry i n the Table, i s the most persistent with a T.y^ of more than 35 days. A l k y l substitution on the carbon between tne sulfur atoms of those molecules containing a n i t r i l e group increases the s o i l persistence. S t i l l , none are as persistent as terbufos. Therefore, the presence of a n i t r i l e i n these molecules, as was previously discussed f o r the Atrazine/ Bladex-triazine relationship, decreases the s o i l persistence of these organophosphorodithioates compared to terbufos.


19.

SANBORN ET AL.


215

F i e l d Evaluation D e s p i t e t h e i r weaker performance i n the laboratory Diabrotica j a r test when compared to terbufos, two of the best compounds of Table 4 were taken to the Midwest for evaluation as s o i l insecticides for control of corn rootworm. The compounds were placed i n the s o i l at planting as a band application at 1 lb/A. During late July and early August the roots were evaluated for corn rootworms damage. A summary of those tests i s collected i n Table 6 along with terbufos as a standard.


Table 6.

F i e l d Performance of Two ates and Terbufos

S-Cyanoalkyl

Phosphorodithio-

S u (C H 0)2-P-SCHSC(CH3) (CN) CH Y 2

5

2

X Structure

X

Site

Y

1

CH. H CH Cl terbufos Untreated

2.7 2.9 2.5 3.2

3

2

3 2.9 3.2 3.5 4.3

2.4 2.5 5.2

4 2.0 2.4 2.3 5.2

5 2.7 3.1 2.4 5.6

Two conclusions can be drawn from the data i n the table. F i r s t l y , the n i t r i l e c o n t a i n i n g p h o s p h o r o d i t h i o a t e s of t h i s study gave insect control i n the order previously estimated from the laborat o r y screen i n that the nonhalogenated molecule gave s l i g h t l y better control than i t s halogenated analogue. Secondly, the nonhalogenated n i t r i l e derivative gave control that was comparable to terbufos. In a l l cases, root ratings for the f i r s t compound i n the table averaged below 3.0 which i s considered to be the economic threshold for this insect. Conclusions This work reports on the effect of incorporation of a n i t r i l e group i n to terbufos and what e f f e c t this group had on i t s laboratory i n s e c t i c i d a l a c t i v i t y and f i e l d performance. With respect to the question regarding e f f i c a c y , we demonstrated that the addition of a n i t r i l e moiety did not markedly reduce the f i e l d performance as compared to terbufos. This was despite a s i g n i f i c a n t l y shorter s o i l h a l f - l i f e as estimated from the l a b o r a t o r y data i n the Diabrotica j a r t e s t . With respect to the question of the effect on the vapor pressure of incorporation of a n i t r i l e into terbufos, the compound ( C H 0 ) ^ ( S ) S Œ ( C H ) S C ( C i O JSÎ£, had an estimated vapor pressure which i s ΐΌ-fold lower (3.0xlu mm) than the measured vapor pressure of terbufos. With respect to a l t e r a t i o n of insect spectra, especially those insects injurious to Midwest f i e l d corn, laboratory studies indicated that l i k e terbufos, only corn root2

5

3


216


worms would be expected to be controlled. Finally, with regards to the estimated cost of manufacture, the addition of a nitrile group to terbufos increases the cost to approximately $2-2.25/lb. This is greater than that for the manufacture of terbufos, but is s t i l l competitive with the other corn-soil insecticides in current use today. Literature Cited


1. 2. 3. 4. 5.

Sanborn, J . R. U.S. Patent 4 505 904 1985. Sanborn, J . R. U.S. Patent 4 536 497 1985. Hoffmann, H.; Hammann, I. U. S. Patent 3 706 820 1972. Godfrey, K. L . ; Saul, G.A. U.S. Patent 2 908 604 1959. Gemrich I I , E. G.; Goldsberry, D.M. J . Econ. Ent. 1982, 220-222.

RECEIVED May 12, 1987


Cyanoalkyl Phosphorodithioates - American Chemical Society

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