N-tertiarybutyl silylamides of the formula ##STR1## WHERE N IS 2 OR 3, ARE EXTREMELY RAPID SILYLATING AGENTS AND ARE ESPECIALLY GOOD FOR SILYLATION IN CONNECTION WITH THE SEPARATION OF COMPLEX MIXTURES. A typical compound is ##STR2## FNT *In this application the following abbreviations are used: t-Bu for the tertiarybutyl radical, Me for the methyl radical, Et for the ethyl radical, Vi for the vinyl radical, Ph for the phenyl radical and i-Pr for the isopropyl radical.

BACKGROUND OF THE INVENTION 
Silylamides are known from U.S. Pat. No. 2,876,209 which shows the 
preparation of amidosilanes by reacting an aminosilane of the formula 
R.sub.4-x Si(NR'R").sub.y, with amides with the removal of the amine 
by-product by volatilization. The amidosilanes produced are of the formula 
##STR3## 
WHERE R' can be alkyl of 1 to 18 carbon atoms such as methyl, ethyl, 
butyl, etc. However, this patent has no specific disclosure of an 
N-t-butylamide either in column 4, line 52, or lines 58-68 where the 
various groups substituted on the nitrogen are elucidated. A 
t-butylsilylamine is one of the starting materials but the t-butyl group 
is removed as t-butyl amine by volatilization. 
A similar disclosure appears in U.S. Pat. No. 2,876,234 which claims the 
amidosilanes. U.S. Pat. No. 3,436,415 discloses the compound 
allylethylbis-N-isopropyl-propionamidesilane, column 2, line 39, and its 
use as an intermediate in the preparation of silyloxazolidones. Also U.S. 
Pat. No. 3,488,371 discloses the compound 
phenylmethylbis-N-(beta-phenylisopropyl)acetamidosilane (Example 5). None 
of these references, however, disclose the N-t-butyl derivative of these 
amidosilanes. 
It is also known that amidosilanes and various other reactive silanes are 
silylating agents which are extensively used in reaction with organic or 
inorganic molecules containing the hydroxyl, the NH or the SH group. In 
general, these silylations are carried out in order to modify the starting 
compounds either in order to carry out additional synthetic steps or in 
order to modify complex mixtures so that they can be more easily 
separated. Additional reasons for silylation are to modify surfaces of 
materials in order to render them hydrophobic and organophilic. 
It is the object of this invention to prepare novel silylamides which are 
much more reactive silylating agents than the best previously known 
silylating agent which is bis-(trimethylsilyl)acetamide. This compound 
silylates quite rapidly, but usually only one of the trimethylsilyl groups 
are employed. The by-product is N-trimethyl-silylacetamide so one half of 
the potential silylating groups are not used. The compounds of this 
invention are some 5 times faster than the bis-trimethyl-silylacetamide 
(BSA) and all of the silicon is used during the silylation. 
The compounds of this invention can be used for silylating any compound 
containing the OH, NH, SH or carboxyl group. They are particularly useful 
in silylating unreactive compounds such as ureas and in the silylation of 
complex mixtures. 
BRIEF DESCRIPTION OF THE INVENTION 
This invention relates to compounds of the formula 
##STR4## 
where n is 2 or 3, R is of the group methyl, ethyl, vinyl, phenyl or 
3,3,3-trifluoropropyl at least 2 R's being methyl when n is 3 and R' is 
methyl or ethyl. 
GENERAL DESCRIPTION OF THE INVENTION 
It should be understood that the compositions of this invention are more 
complex than the simple formula shown above. It is generally believed that 
silylated amides are actually an equilibrium mixture of tautomeric 
materials represented by the equation 
##STR5## 
In other words, it is believed that the compounds are mixtures of the 
amide and imidate form of these materials. Consequently, it should be 
understood that this application and the claims in this application cover 
both forms of the molecules and mixtures thereof. 
The compositions of this invention where n is 3 are best prepared by 
reacting the chlorosilane of the formula R.sub.3 SiCl with the 
corresponding N-t-butylamide in the presence of a tertiary amine as a 
hydrogen halide acceptor. This reaction proceeds readily at room 
temperature and the amine hydrochloride salt is removed by filtration or 
other suitable means and the silylated amide is obtained by distillation 
or other suitable means. The compositions of this invention where n is 2 
are best prepared by reacting a silane of the formula R.sub.2 SiCl.sub.2 
with the corresponding compound 
##STR6## 
under conditions where the triorganochlorosilane is removed from the 
reaction zone. This reaction will generally occur at ambient temperature 
and the R.sub.3 SiCl can be removed at reduced pressure.

The following examples are illustrative only and should not be construed as 
limiting the invention which is properly delineated in the appended 
claims. 
EXAMPLE 1 
A dry flask was fitted with a reflux condenser, stirring bar and septum and 
evacuated and flushed with dry nitrogen. The flask was protected from 
moisture with nitrogen and a series of dry ice traps. The flask was 
charged with 20 g. of sublimed N-t-butylacetamide, 118.39 g. of 
triethylamine and 50 ml. of dry pentane. 37.73 g. of trimethylchlorosilane 
was added to the stirred solution through a syringe. A slight exotherm was 
noted along with the precipitation of triethylamine hydrochloride. The 
mixture was allowed to stir overnight and the slurry was centrifuged. The 
organic liquid was filtered and the salts washed with dry pentane. The 
combined organic liquids were distilled to give a 61.7 percent yield of 
##STR7## 
boiling at 62.degree. C at 22 mm of mercury. The structure of the compound 
was verified by infrared analysis and nmr analysis. 
EXAMPLE 2 
The relative reactivity of the various N-alkyl substituted 
trimethylsilyacetamides was determined by reacting each with 
N-butylacetamide. This reaction goes in accordance with the following 
equation: 
##STR8## 
The amount of D produced at equilbrium is a measure of the reactive 
reactivity of A with respect to D and the reactivity of A is a function of 
the equilibrium constant K/eg. The latter were obtained as follows: A dry 
septumed vial was charged with about 0.8 g. of dry acetonitrile and then 
equimolar amounts (about 2.7 .times. 10.sup.-3 mols) of A and B were 
added. Samples were periodically removed from the mixture for gas liquid 
chromatography analysis. The entire operation was carried out at ambient 
temperature. The weight of product was calculated by the formula: weight 
of product = (A/A.sub.i) .times. (W.sub.i /W) where A.sub.1 is the area of 
the compound, A was the area of the acetonitrile, W.sub.i was the weight 
of the compound and W was the weight of the acetonitrile. 
The gas liquid chromatograms were taken on an Infotronics Model 2400 Series 
gas chromatograph equipped with a Model 68 linear temperature programmer 
and a 6 ft. by 1/8 inch (182.88 cm. by 3.18 mm) packed with diatomaceous 
earth of 100 to 120 mesh coated with 5% by weight of a 
trifluoropropylmethyl siloxane of 10,000 cs viscosity (designated SP-2401 
by Supelco Incorporated). The injection port temperature was maintained at 
200.degree. C and the detector (He) at 310.degree. C. The column was 
linearly programmed at 20.degree. C/min. from 100.degree. to 200.degree. C 
with a chart speed of 2 min./inch. (2.45 cm). 
Runs 2 to 5 are for purpose of comparison. 
______________________________________ 
Run No. 
Silylamide A K.sub.eg * 
______________________________________ 
(1) 
##STR9## 110.00 
(2) 
##STR10## 22.00 
(3) 
##STR11## 1.00 
(4) 
##STR12## 0.30 
(5) 
##STR13## 0.00093 
______________________________________ 
##STR14## 
This data shows that the N-t-butyltrimethyl-silylacetamide of this 
invention is 5 times faster than the best previously known silylating 
agent (2); is 110 times faster than the corresponding n-butyl compound 
(3); is 366 times faster than the N-methyl compound (4); and is 100,000 
times faster than the N-isopropyl derivative (5). 
EXAMPLE 3 
Into a dry flask equipped with a stirrer, distillation head and septum was 
added 5 g. of freshly distilled 
##STR15## 
and 1.72 g. of freshly distilled dimethyldichlorosilane. The system was 
evacuated at ambient temperature and trimethylchlorosilane was removed at 
ambient temperature. The product 
##STR16## 
was obtained in 91 percent yield. The product was reacted with methanol at 
room temperature and the amount of dimethyldimethoxysilane and 
t-butylacetamide produced were determined by infrared and nmr analysis. 
This procedure showed the product to be pure. 
EXAMPLE 4 
Using the procedure of Example 1, the following compounds can be prepared 
by reacting the following silanes with the following N-t-butylamides. 
______________________________________ 
Silane N-t-butylamide 
product 
______________________________________ 
PhMe.sub.2 SiCl 
##STR17## 
##STR18## 
EtMe.sub.2 SiCl 
##STR19## 
##STR20## 
ViMe.sub.2 SiCl 
##STR21## 
##STR22## 
(CF.sub.3 CH.sub.2 CH.sub.2)Me.sub.2 SiCl 
##STR23## 
##STR24## 
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