Tris(triorganosilylalkyl) phosphites and method for preparing them

A novel class of compounds, tris(triorganosilylalkyl) phosphites, represented by the general formula [R.sub.3 Si(CH.sub.2).sub.n O].sub.3 P where R is a monovalent hydrocarbon group and n is 1, 2 or 3. These novel compounds may be synthesized by dehydrochlorination reaction between a triorganosilyl-substituted alkanol and phosphorus trichloride in the presence of a tertiary amine. They have useful values as agricultural chemicals because of their biological activities and also as intermediate compounds in the preparation of certain medicines and chemicals.

FIELD OF THE INVENTION 
The present invention relates to a novel class of tris(triorganosilylalkyl) 
phosphites containing a number of silicon atoms and a phosphorus atom in 
the molecule. The invention relates also to a method of preparing the 
novel compounds. 
SUMMARY OF THE INVENTION 
The novel class of compounds provided herein are tris(triorganosilylalkyl) 
phosphites that have not been known and disclosed in any literature. The 
novel compounds are represented by the general formula 
EQU [R.sub.3 Si(CH.sub.2).sub.n O].sub.3 P 
where R is a substituted or unsubstituted monovalent hydrocarbon group and 
n is a positive integer. 
According to the present invention, the novel tris(triorganosilylalkyl) 
phosphites may be prepared by dehydrochlorination reaction between a 
triorganosilylalkanol and phosphorus trichloride in the presence of a 
dehydrochlorinating agent, such as a tertiary amine. 
The novel compounds have biological activities suitable for agricultural 
chemicals. They are also useful as intermediate compounds in the synthetic 
preparation of certain organic compounds including medicines. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the general formula [R.sub.3 Si(CH.sub.2).sub.n O].sub.3 P representing 
the novel tris(triorganosilylalkyl) phosphites of the present invention, 
the groups represented by symbol R being substituted or unsubstituted 
monovalent hydrocarbon groups, each being the same or different, are 
exemplified by alkyl groups, such as methyl, ethyl, propyl and butyl 
groups; alkenyl groups, such as vinyl and allyl groups; aryl groups, such 
as phenyl group; and those substituted monovalent groups by halogen atoms 
or other substituents in place of part or all of the hydrogen atoms in the 
above-named hydrocarbon groups and n is a positive integer or, in 
particular, 1, 2 or 3. 
The examples belonging to the novel class of tris(triorganosilylalkyl) 
phospites within the above definition include the following compounds. 
EQU [(CH.sub.3).sub.3 SiCH.sub.2 O].sub.3 P (1) 
EQU [(ch.sub.3).sub.3 si(CH.sub.2).sub.3 O].sub.3 P (2) 
EQU [c.sub.4 h.sub.9 (ch.sub.3).sub.2 siCH.sub.2 O].sub.3 P (3) 
EQU [ch.sub.2 .dbd.ch(ch.sub.3).sub.2 siCH.sub.2 O].sub.3 P (4) 
EQU [c.sub.6 h.sub.5 (ch.sub.3).sub.2 siCH.sub.2 O].sub.3 P (5) 
EQU [clCH.sub.2 (CH.sub.3).sub.2 SiCH.sub.2 O].sub.3 P (6) 
the novel tris(triorganosilylalkyl) phosphites of the present invention may 
be prepared by several methods. For example, the compounds are synthesized 
by dehydrochlorination reaction between a triorganosilylalkanol 
corresponding to the desired phosphite and phosphorus trichloride in the 
presence of a tertiary amine as a dehydrochlorinating agent, such as 
trialkyl amines represented by the general formula R'.sub.3 N where R' is 
an alkyl group. 
As a further example, the novel compounds are produced by reacting an 
alkali metal, e.g. sodium or potassium salt of the triorganosilylalkanol 
with phosphorus trichloride in a suitable solvent with the formation of 
alkali chloride, e.g. NaCl or KCl. 
Of the above two methods preferred is the former with respect of easiness 
in the synthetical operation as well as yield of product. 
The reaction taking place in the former method is expressed by the 
following equation: 
EQU R.sub.3 Si(CH.sub.2).sub.n OH + PCl.sub.3 + 3R'.sub.3 N 
EQU .fwdarw. [r.sub.3 si(CH.sub.2).sub.n O].sub.3 P + 3R'.sub.3 N.multidot.HCl 
where R, R' and n are as defined herein above. 
This reaction can be carried out by dropping a solution of phosphorus 
trichloride in an inert solvent into a mixture of the 
triorganosilylalkanol and the tertiary amine, optionally diluted with an 
inert solvent, under cooling, and, if necessary, and advantageously, by 
heating under reflux after the dropping is over. Subsequently amine 
hydrochloride which has been produced as a by-product is removed from the 
reaction mixture, and the resulting liquid portion is subjected to 
distillation, to finally obtain the desired tris(triorganosilylalkyl) 
phosphite. 
The triorganosilylalkanols as the starting material in the above reaction 
are readily obtained by conventional methods. An example for the syntheses 
of the alkanol compound (CH.sub.3).sub.3 SiCH.sub.2 OH is the following. 
##STR1## 
Another example for the synthesis of the alkanol compound (CH.sub.3).sub.3 
Si(CH.sub.2).sub.3 OH is the following. 
##STR2## 
Illustrative of the tertiary amines used as the dehydrochlorinating agent 
in the reaction for the preparation of the tris(triorganosilylalkyl) 
phosphite of the present invention are triethylamine, pyridine, 
.alpha.-picoline, and tri(n-butyl)amine. Illustrative of suitable inert 
solvents are aromatic hydrocarbon solvents, such as benzene and toluene; 
aliphatic hydrocarbon solvents, such as hexane and octane; and ethers, 
such as diethyl ether and dibutyl ether. 
The amounts of the triorganosilylalkanol and the tertiary amine used are 
each desired to be more than 3 moles per mole of phosphorus trichloride to 
be brought into reaction with them. 
The temperature at which the reaction is carried out should be in the range 
from -20 to +150.degree. C or, preferably, from 0 to +50.degree. C. 
The novel tris(triorganosilylalkyl) phosphites of the present invention are 
in general odorless in contrast to ordinary alkyl phosphites which have 
characteristic, unpleasant odor. They being biologically active compounds 
have an insecticidal activity against the noxious insects in rice crops, 
such as rice stem borers (larvae of Chilo Suppressalis Walker) and green 
rice leafhoppers (Nephotettix cincticeps Uhler). They are also useful as 
intermediate compounds in the synthetical preparation of various kinds of 
medicines and agricultural chemicals. Furthermore, they are effective as 
flame retardants when incorporated in plastic materials.

Further details of the synthesis of the novel compounds in accordance with 
the present invention and the identification of them will be apparent from 
the following examples. 
EXAMPLE 1 
Into a glass flask of 1 liter capacity provided with a stirrer, a 
thermometer and a reflux condenser were introduced 192 g (1.84 moles) of 
trimethylsilylmethyl alcohol, 202 g (2.00 moles) of triethylamine and 300 
ml of benzene. The flask was submerged in an ice water bath. A solution of 
80 g (0.58 moles) of phosphorus trichloride in 200 ml of benzene was 
dropped into the mixture in the flask over a period of about 2 hours. 
During the reaction the temperature of the reaction mixture was maintained 
between 0.degree. and 10.degree. C. The thus treated reaction mixture was 
then heated under reflux for 3 hours, to complete the intended reaction. 
Thereupon the reaction mixture was filtrated to remove triethylamine 
hydrochloride as a by-product, and the resulting filtrate was subjected to 
distillation to obtain 163.2 g of a product with fractional boiling at 
89.degree. to 91.degree. C under the reduced pressure of 1.5 mmHg. 
The product obtained above was subjected to elementary analysis, NMR 
spectral analysis, and measurement of density and refractive index. The 
results were as follows. 
Elementary analysis: 
______________________________________ 
As calculated, as 
As measured [(CH.sub.3).sub.3 SiCH.sub.2 O].sub.3 P 
______________________________________ 
Si 24.80% 24.74% 
C 42.35% 42.31% 
H 9.73% 9.77% 
O 14.12% 14.09% 
P 9.13% 9.09% 
NMR spectrum: 
(CH.sub.3).sub.3 -- 
0.10 (.delta.) singlet 
.tbd.SiCH.sub.2 OP.dbd. 
3.23 (.delta.) doublet 
Density, d.sub.4.sup.20 : 
0.8856 
Refractive index 
n.sub.D.sup.25 : 
1.4365 
______________________________________ 
It was concluded from the above data that the product was a compound 
expressed by the structural formula [(CH.sub.3).sub.3 SiCH.sub.2 O].sub.3 
P. The yield of product was 82.6% of the theoretical. 
EXAMPLE 2 
The same flask as used in Example 1 was charged with 132 g (1.00 mole) of 
trimethylsilylpropyl alcohol, 152 g (1.50 moles) of triethylamine and 300 
ml of benzene, and the flask was submerged in an ice water bath. Then a 
solution of 41.2 g (0.3 moles) of phosphorus trichloride in 200 ml of 
benzene was dropped into the mixture in the flask over a period of about 2 
hours, throughout which the temperature of the reaction mixture remained 
between 0.degree. and 10.degree. C. The thus treated reaction mixture was 
then heated under reflux for 3 hours, to complete the intended reaction. 
Thereupon the reaction mixture was filtrated to remove triethylamine 
hydrochloride as a by-product, and the resulting filtrate was subjected to 
distillation to obtain 93.2 g of a product with fractional boiling at 
158.degree. to 159.degree. C under the reduced pressure of 1.0 mmHg. 
The product thus obtained was subjected to elementary analysis, NMR 
spectral analysis, and measurement of density and refractive index, with 
the results shown below. 
Elementary analysis: 
______________________________________ 
As calculated, as 
As measured [(CH.sub.3).sub.3 Si(CH.sub.2).sub.3 O].sub.3 
______________________________________ 
P 
Si 19.80% 19.84% 
C 50.92% 50.90% 
H 10.70% 10.68% 
O 11.28% 11.29% 
P 7.30% 7.29% 
NMR spectrum: 
(CH.sub.3).sub.3 Si-- 
0.04 (.delta.) singlet 
.tbd.SiCH.sub.2 OP.dbd. 
3.58 (.delta.) quartet 
Density, d.sub.4.sup.20 : 
0.8764 
Refractive index; 
n.sub.D.sup.25 : 
1.4481 
______________________________________ 
It was concluded from the above data that the product was a compound 
expressed by the structural formula [(CH.sub.3).sub.3 Si(CH.sub.2).sub.3 
O].sub.3 P. The yield was 73.2% of the theoretical. 
EXAMPLE 3 
The same flask as used in Example 1 was charged with 146 g (1.00 mole) of 
n-butyldimethylsilylmethyl alcohol, 152 g (1.50 moles) of triethylamine 
and 300 ml of benzene, and the flask was submerged in an ice water bath. 
Then a solution of 41.2 g (0.3 moles) of phosphorus trichloride in 200 ml 
of benzene was dropped into the mixture in the flask over a period of 
about 2 hours, throughout which the temperature of the reaction mixture 
was maintained between 0.degree. and 10.degree. C. The thus treated 
reaction mixture was then heated under reflux for 3 hours, to complete the 
intended reaction. Thereupon the mixture was filtrated to remove 
triethylamine hydrochloride as a by-product, and the resulting filtrate 
was subjected to distillation to obtain 113.8 g of a product with 
fractional boiling at 163.degree. to 166.degree. C under the reduced 
pressure of 1.0 mmHg. 
The product thus obtained was subjected to elementary analysis, NMR 
spectral analysis and measurement of density and refractive index with the 
following results. 
Elementary analysis: 
______________________________________ 
As calculated, as 
As measured [C.sub.4 H.sub.9 (CH.sub.3).sub.2 SiCH.sub.2 
O].sub.3 P 
______________________________________ 
Si 18.06% 18.05% 
C 54.03% 54.03% 
H 11.05% 11.01% 
O 10.30% 10.28% 
P 6.66% 6.63% 
NMR spectrum: 
--(CH.sub.3).sub.2 Si-- 
0.10 (.delta.) singlet 
.tbd.SiCH.sub.2 OP.dbd. 
3.23 (.delta.) singlet 
Density, d.sub.4.sup.20 : 
0.8834 
Refractive index, 
n.sub.D.sup.25 : 
1.4521 
______________________________________ 
It was concluded from the above data that the product was a compound 
expressed by the structural formula [C.sub.4 H.sub.9 (CH.sub.3).sub.2 
SiCH.sub.2 O].sub.3 P. The yield was 81.3% of the theoretical.