An acetylenic end-capping agent of the general formula ##STR1## wherein R.sup.1 and R.sup.2 can be the same or different and are selected from the group consisting of hydrogen, C11 to C4 alkyl, phenyl and substituted phenyl, and wherein R.sup.1 and R.sup.2 together with the carbon atom to which they are attached form a saturated 5- or 6-membered ring. This end-capping agent is substantially free of Pd and Cu. Also provided is a method for producing this end-capping agent and a method for producing acetylene terminated compounds.

BACKGROUND OF THE INVENTION 
The present invention is directed to .alpha.-hydroxy-, 
.alpha.-alkyl-substituted acetylene compounds. 
Epoxy matrix composites have been widely used in aerospace products. 
However, epoxy matrix systems have drawbacks, not the least of which is 
that such systems are sensitive to moisture. Extended exposure to high 
humidity reduces the mechanical properties of cured epoxy systems at 
elevated temperatures. Accordingly, there has been considerable interest 
in polymers that could replace epoxies and which are significantly less 
sensitive to moisture, but which retain the desirable characteristics of 
the epoxies. 
A variety of acetylene-terminated resin systems have been prepared and 
studied in recent years. Acetylene-terminated resins cure through addition 
rather than condensation, thus avoiding the problem of voids caused 
primarily by outgassing which occurs during the condensation mechanism 
cure. 
One procedure for adding terminal acetylene groups to an oligomer comprises 
reacting the oligomer with a substituted terminal acetylene compounds 
containing at least three carbon atoms with an hydroxy group on the carbon 
atom adjacent the acetylene group, which may be converted to the desired 
acetylene terminated oligomer by base catalyzed cleavage. The preparation 
of acetylene terminated sulfone oligomers by this method is described in 
U.S. Pat. No. 4,356,325 to Harrison et al. The reaction of the sulfone 
with the terminal acetylenic compound is carried out in the presence of a 
palladium salt complex catalyst system and a cuprous salt promoter. A 
major problem associated with this process is removal of the metallic 
salts after the displacement reaction. Removal of both Pd and Cu to less 
than 20 ppm must be accomplished; otherwise premature crosslinking of the 
acetylene groups can take place leading to poor mechanical performance. 
Although treatment with a dialkyl or trialkyl-amine does remove these 
metals in monomeric small molecules, it is extremely difficult to remove 
the metals from higher molecular weight oligomers. 
Another procedure for adding terminal acetylene groups to an oligomer 
comprises reacting the oligomer with the metallic salt of 
m-hydroxyphenylacetylene, as disclosed in U.S. Pat. No. 4,108,926 to 
Arnold et al. The metallic salt is, however, difficult to synthesize and 
expensive to produce. The synthesis comprises treatment of 
3-hydroxyacetophenone with tosyl chloride to form the tosylated 
acetophenone, which is thereafter treated with phosphorus oxychloride and 
DMF to form .alpha.-chlorocinnamaldehyde-3-yl(p-toluenesulfonate). 
Hydrolysis of the latter compound with KOH yields the potassium salt of 
m-hydroxyphenylacetylene. 
Accordingly, it is an object of the present invention to provide a new 
method for adding terminal acetylene groups to a molecule. 
Another object of the present invention is to provide a novel acetylenic 
end-capping agent for oligomers. 
A further object of the present invention is to provide a method for 
preparing novel acetylenic end-capping agents. 
Other objects, aspects and advantages of the present invention will be 
apparent to those skilled in the art from a reading of the following 
disclosure. 
SUMMARY OF THE INVENTION 
In accordance with the present invention there is provided a novel 
acetylenic end-capping agent having the general formula: 
##STR2## 
wherein R.sup.1 and R.sup.2 can be the same or different and are selected 
from the group consisting of hydrogen, C1 to C4 alkyl, phenyl, and 
substituted phenyl, and wherein R.sup.1 and R.sup.2 together with the 
carbon atom to which they are attached form a saturated 5- or 6-membered 
ring. 
Also provided in accordance with the invention is a method for preparing 
the above-described acetylenic end-capping agent. The method comprises 
reacting an m-halophenol with an acetylenic compound of the general 
formula 
##STR3## 
wherein R.sup.1 and R.sup.2 are as described above, in the presence of a 
dialkyl or trialkyl amine solvent, a Pd complex catalyst system and a 
cuprous salt promoter. 
Further, in accordance with the present invention, there is provided a 
method for adding terminal acetylene groups to a molecule which comprises 
reacting a halogen-terminated molecule with the above-described 
end-capping agent followed by base-catalyzed cleavage. 
DETAILED DESCRIPTION OF THE INVENTION 
As stated above, the end-capping agent of the present invention has the 
general formula 
##STR4## 
wherein R.sup.1 and R.sup.2 can be the same as different and are selected 
from the group consisting of hydrogen, C1 to C4 alkyl, phenyl, substituted 
phenyl, and wherein R.sup.1 and R.sup.2 together with the carbon atom to 
which they are attached form a saturated 5- or 6-membered ring. 
The end-capping agent is prepared by reacting a halophenol of the general 
formula 
##STR5## 
wherein X is --F, --Cl or --Br, with an acetylenic compound of the general 
formula 
##STR6## 
wherein R.sup.1 and R.sup.2 are as described above, in the presence of a 
diakyl or trialkyl amine solvent, a Pd complex catalyst system and a 
cuprous salt promoter. Suitable acetylenic compounds include the 
following: 2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol, 
3-ethyl-1-pentyn-3-ol, 2-phenyl-3-butyn-2-ol, 1-ethynylcyclopentanol, and 
1-ethynylcyclohexanol. The preparation of these compounds is well known in 
the art and forms no part of the present invention. 
The amine solvent has the formula: 
##STR7## 
wherein R.sup.3, R.sup.4 and R.sup.5 can be the same or different and are 
selected from the group consisting of hydrogen and C1-C4 alkyl, with the 
proviso that no more than one of the R groups can be hydrogen. Suitable 
solvents include but are not limited to dimethylamine, trimethylamine, 
diethylamine, triethylamine, dipropylamine, tripropylamine, 
di-n-butylamine, tri-n-butylamine, ethylpropylamine, and the like, as well 
as mixtures thereof. 
The catalyst employed is a complex palladium salt containing two halogen 
moieties, wherein the halogen is selected from the group consisting of 
--Br, --Cl and --I, and two trisubstituted phosphine moieties wherein the 
constituents are selected from the group consisting of phenyl, C1-C4 
alkyl, and substituted phenyl groups. The substituents on the phenyl 
groups can include C1-C4 alkyl, C1-C4 alkoxy, and halogen. Examples of 
suitable palladium complex salts include the following: 
bis(triphenylphosphine)palladium dichloride, 
bis(triphenylphosphine)palladium dibromide, 
bis(tri-n-butylphosphine)palladium dichloride, 
bis(tri-t-butylphosphine)palladium dichloride, 
bis(tri-i-butylphosphine)palladium dichloride, 
bis(triethylphosphine)palladium dichloride, 
bis(tripropylphosphine)palladium dichloride, 
bis(tritolylphosphine)palladium dichloride, 
bis(trianisylphosphine)palladium dichloride, 
bis(tri(chlorophenylphosphine)palladium dichloride and 
bis(tri(bromophenyl)phosphine)palladium dichloride, and the like. 
The promoter comprises cuprous salts such as cuprous iodide, cuprous 
chloride, copper acetylacetonate, cuprous bromide, and the like. 
Generally, the amount of the promoter is very small, and suitable amounts 
of promoter include a molar ratio of promoter to palladium catalyst of 
about 0.5:1 to 20:1, preferably about 1:1 to 5:1. The amount of the 
palladium catalyst employed in the reaction is about 0.01 to 1.0 mole 
percent based on the halophenol, preferably about 0.10 to 0.30 mole 
percent. 
It is desirable to include together with the catalyst/promoter system a 
trisubstituted phosphine, preferably the same trisubstituted phosphine as 
that which is a part of the complex palladium salt. Generally, the weight 
ratio of such trisubstituted phosphine to the complex palladium salt can 
range from about 0.25:1 to 4:1. 
The halophenol and the acetylenic compound react to form the end-capping 
agent of the present invention as follows: 
##STR8## 
The reaction conditions to employ are relatively mild and include a 
temperature of about 20.degree. to 200.degree. C., preferably about 
50.degree. to 100.degree. C. The reaction conditions should be such that 
the solvent chosen is maintained in the liquid phase. The normal reaction 
pressure is atmospheric; however, increased reaction pressures of up to 
250 psig (1.7 MPa) or higher may be used. The reaction time to employ is 
somewhat dependent upon the charge stock and catalyst chosen, as well as 
the reaction temperature. Generally, the reaction time is from one hour to 
150 hours, but usually from about 3 hours to about 30 hours. 
The resulting protected ethynylated acetylated phenol is subjected to a 
metals removal and purification operation for removal of the palladium and 
copper metal contaminants. A suitable metals removal system involves the 
use of a combination of a hydrogen halide-treatment step followed by a 
metals complexing step using an amino compound. The method comprises 
admixing a solution containing the metal-contaminated acetylated phenol 
with an aqueous hydrogen halide, e.g., hydrochloric acid, hydrobromic 
acid, or the like, including mixtures thereof, and then removing the 
hydrogen halide. Next, the solution is contacted with an amino compound, 
such as ammonia in the form of ammonium hydroxide, polyamines, such as 
ethylenediamine, ethylenetriamine, or the like, to form complexes with the 
metal contaminants, which can be separated from the protected ethynylated 
phenol by washing the solution with water. The levels of palladium and 
copper can be reduced to less than 5 ppm. 
The metal-contaminated protected ethynylated phenol can be contacted with 
the hydrogen halide under any suitable conditions, preferably ambient 
temperature and pressure. Similarly, the acid-treated solution can be 
contacted with the amino compound to form the metal complexes under any 
suitable conditions including a temperature in the range of about 
40.degree. C. to about 100.degree. C., preferably about 
50.degree.-70.degree. C. for a period of about 0.1 to about 2 hours, 
preferably about 0.25 to 1 hour. Atmospheric or increased pressure can be 
used as desired. 
The protected ethynylated phenols of this invention are useful as 
end-capping agents for a variety of monomers and oligomers. For example, 
such compounds can be used for the preparation of thermosetting 
acetylene-terminated sulfone resins. The sulfones can be prepared 
according to the general reaction: 
##STR9## 
wherein Ar is a divalent aromatic radical such as 
##STR10## 
and the like, X is --Cl, --F or --Br, and n is an integer corresponding to 
the number of recurring units. The value of n can vary within a broad 
range, e.g., from 1 to about 200. 
The phenylenesulfones are well known in the art. They can be readily 
prepared by the solution condensation of a dialkali metal salt of a 
dihydric phenol with a dihalo aromatic diphenylsulfone in an anhydrous 
dipolar aprotic solvent at elevated temperatures. The metal salt may be 
prepared in situ. 
The protected ethynylated phenol end-capping agent of this invention is 
reacted with a desired molecule in a suitable solvent in the presence of 
an alkali metal alkoxide. This reaction may be represented as follows: 
##STR11## 
wherein X, R.sup.1 and R.sup.2 are as previously described. 
Suitable solvents include dimethylsulfoxide, N-methylpyrolidone, 
bis-methoxy ethoxy diethyl ether, tetrahydrothiophene-1,1-dioxide, and the 
like. Suitable alkali metal alkoxides include potassium methoxide, 
potassium ethoxide, cesium ethoxide, and the like. 
The reaction of the protected ethynylated phenol with the desired molecule 
can be conducted under any suitable conditions easily determined by those 
skilled in the art. The reaction conditions should be such that the 
solvent chosen is maintained in the liquid phase. The normal reaction 
pressure is atmospheric; however, increased reaction pressures of up to 
250 psig or higher can be employed. Suitable temperatures include those in 
the range of about 50.degree. to 150.degree. C. The reaction time is 
somewhat dependent, inter alia, upon the particular charge stock and the 
reaction temperature. Suitable reaction times include from about 1 to 
about 50 hours. 
The hydroxy-acetylene terminated phenoxy-molecule produced in Reaction 
(III) is then subjected to base catalyzed cleavage to form the desired 
acetylene terminated molecule as follows: 
##STR12## 
wherein R.sup.1 and R.sup.2 are as previously defined. 
Base catalyzed cleavage is carried out under any suitable reaction 
conditions, such as a temperature in the approximate range of 50.degree. 
to 150.degree. C., preferably about 90.degree. to 120.degree. C., in the 
presence of a suitable base, such as KOH or NaOH, for 0.5 to 20 hours. 
Where the desired molecule is a sulfone, as previously described, the above 
reactions proceed as follows: 
##STR13## 
wherein X, n, R.sup.1 and R.sup.2 are as previously defined. 
The protected ethynylated phenol end-capping agents of the present 
invention may be used to prepare a variety of acetylene terminated 
monomers and oligomers, including sulfones, as described above, polyimide 
oligomers, polyarylene oxide oligomers, poly(2,6-benzothiazole)oligomers 
and the like. Inasmuch as both palladium and copper are removed to very 
low levels prior to end capping the monomers or oligomers the problem of 
premature crosslinking due to the presence of these metals is effectively 
nonexistent. 
The following examples illustrate the invention.

EXAMPLE I 
Preparation of 3-hydroxyphenyl-2-methyl-3-butyn-2-ol 
A 3-necked 500 ml round-bottomed flask was fitted with reflux condenser, 
magnetic stir bar, stopper, and gas inlet/outlet adapters. Under dry 
nitrogen the flask was charged with 3-bromophenol (10.0 g, 57.8 mmol), 
2-methyl-3-butyn-2-ol (5.0 g, 59.4 mmol) and 250 ml of distilled 
triethylamine. The mixture was heated at reflux for 15 minutes while 
nitrogen was bubbled into the solution. To the yellow solution was added 
dichlorobis(triphenyl)phosphone)palladium II (0.2 g) which was allowed to 
go completely into solution, triphenylphosphine (0.2 g) and cuprous iodide 
(0.1 g). The reaction was heated at reflux under nitrogen for 25 h. 
After the reaction mixture was cooled to 25.degree. C., using an ice/water 
bath, it was filtered through a glass frit packed with celite under 
nitrogen. The remaining light gray ppt was rinsed with additional 
triethylamine and the fractions combined. The golden yellow filtrate was 
concentrated (rotary evaporator) and the resulting yellow oil dissolved in 
200 ml of toluene and then washed with 120 ml of 8% hydrochloric acid 
(aqueous). Next the hydrochloric acid washing was extracted with three 50 
ml portions of ethyl acetate, the fractions combined, concentrated (rotary 
evaporator) and dissolved in 25 ml of toluene. The toluene fractions were 
combined and dried (magnesium sulfate). To the dry toluene solution 50 ml 
of ethylene diamine was added, turning the solution brown. While bubbling 
nitrogen through the mixture, the solution was stirred and heated 
(50.degree.-60.degree. C.) for 15 minutes. During this procedure a blue 
ppt formed. After cooling to room temperature, the solution was filtered 
to remove the ppt. The filtrate was next extracted with 250 ml of 
distilled water and then with three 125 ml portions of 10% potassium 
carbonate (aqueous). The extract was stirred in an ice/water bath and 
neutralized with 50% hydrochloric acid (aqueous). The acid addition was 
continued until the pH was slightly acidic. The aqueous solution was next 
extracted with one 250 ml portion of ethyl acetate and then three 125 ml 
portions, dried (magnesium sulfate), filtered and concentrated (rotary 
evaporator). The resulting dark yellow-orange oil was induced to 
crystallize by dissolving in methylene chloride, adding n-hexane until 
slightly cloudy, seeding, and cooling by refrigeration for 24 h. 
Recrystallizations were repeated until the product was white. The final 
procedure yielded 4.1 g (41%) of pure product mp: 94.degree.-95.degree. C. 
Analysis for C.sub.11 H.sub.12 O.sub.2 : Calc'd: C,74.91; H,6.81. Found: 
C,74.52; H,6.96. 
Analysis for Cu and Pd was found to be less than 3 ppm of each. 
EXAMPLE II 
Preparation of sulfone monomer and oligomer 
A 3-necked, 250 ml, round bottom flask, was equipped with magnetic stir 
bar, reflux condenser, dean-start trap, and gas inlet/outlet adapters. To 
the reaction flask the following mixture was added: 4,4'-thiodiphenol (4.0 
g, 18.0 mmol), difluorodiphenyl sulfone (18.61 g, 73.0 mmol), anhydrous 
potassium carbonate (2.53 g, 18.0 mmol), 35 ml of freshly distilled 
N-methyl-1-pyrrolidone and 30 ml of benzene. The reaction mixture was 
heated at reflux (100.degree. C.) and stirred rapidly under dry nitrogen 
until all water (a reaction side product) was essentially removed from the 
system by azeotropic distillation with benzene. The reaction (light purple 
in color) temperature was then raised and maintained at 120.degree. C. for 
4 h. The mixture darkened slightly during this period. After cooling to 
40.degree. C., the reaction mixture was diluted with 100 ml of methylene 
chloride and washed with three 200 ml portions of 10% hydrochloric acid 
(aqueous) and one 400 ml portion of distilled water, dried (magnesium 
sulfate) and filtered. The filtrate was concentrated (rotary evaporator) 
and chromatographed on a quartz column filled with activated silica gel 
(500 g). Unreacted difluorodiphenyl sulfone was eluted with 
n-hexane/chloroform (4/1), the product monomer was eluted with 
n-hexane/chloroform (1/1) to yield 6.18 g of (I) a white crystalline 
solid: mp 116.degree.-118.degree. C. The product oligomer was eluted with 
ChCl.sub.3 to yield 5.07 g of (II) a light yellow viscous oil. Total 
product yield was 11.25 g (89.4%). 
Analysis for C.sub.36 H.sub.24 O.sub.6 S.sub.3 F.sub.2 : Calc'd: C,62.92; 
H,3.50; S,14.01. Found: C,62.74; H,3.57; S,13.95. 
EXAMPLE III 
Preparation of Acetylene Terminated Sulfone 
A 3-necked, 50 ml round bottom flask was equipped with magnetic stir bar 
and gas inlet/outlet adapters. Under dry nitrogen the flask was charged 
with 4-hydroxyphenyl-1-methyl-3-butyn-2-ol (1.63 g, 9.2 mmol) and 40 ml of 
dimethylsulfoxide. To this solution potassium methoxide (0.65 g, 9.2 mmol) 
was added. The mixture was stirred for 1 h at 25.degree. C., transferred 
to an addition funnel under nitrogen, and added over a period of 1 h to a 
solution of (I) (3 g, 4.4 mmol) in 40 ml of dimethylsulfoxide stirred at 
85.degree. C. When addition was complete, the reaction mixture temperature 
was maintained at 85.degree. C. for an additional 4 hours, after which it 
was cooled to 25.degree. C. and the mixture stirred overnight under 
nitrogen. Next the reaction mixture was diluted with 150 ml of methylene 
chloride and washed with three 300 ml portions of 10% hydrochloric acid 
(aqueous) dried (magnesium sulfate) and filtered. The filtrate was 
concentrated (by rotary evaporator) and chromatographed on a quartz column 
filled with activated silica gel (180 g). The product was eluted with 
ethyl acetate/chloroform (1/9) to yield 3.16 g (68.7%) of (III) a white 
solid: mp 156.degree.-157.degree. C. 
Analysis for C.sub.58 H.sub.46 O.sub.10 S.sub.3 : Calc'd: C,69.68; H,4.61; 
S,9.63. Found: C,67.33; H,4.64; S,9.26. 
While heating under nitrogen (III) (2.0 g, 2.0 mmol) was dissolved in 60 ml 
of dry benzene contained in a 3-necked, 250 ml round bottomed flask. The 
reaction flask was equipped with a dean-stark trap, reflux condenser, 
magnetic stir bar and gas inlet/outlet adapters. After (III) was observed 
to go completely into solution, 50 ml of 10% methanolic potassium 
hydroxide was added and the mixture stirred and heated at reflux for 1 h. 
Acetone formed as the reaction progressed and was removed from the system 
along with half of the original volume of benzene. The lost volume of 
benzene was replaced and the distillation procedure repeated three more 
times (replacing the lost volume of benzene the first and second times). 
The progress of the reaction was followed by TLC on silica gel with 
methylene chloride. After 4 h, the reaction mixture was cooled to 
25.degree. C., filtered over celite and washed with three 100 ml portions 
of distilled water, dried (magnesium sulfate) and filtered. The filtrate 
was concentrated (rotary evaporator) and chromatographed on a quartz 
column filled with activated silica gel (160 g). The product was eluted 
with hexane/chloroform (1/1) to yield 1.39 g (79%) of (IV) a fluffy white 
solid: mp 91.degree.-94.degree. C. 
Analysis for C.sub.25 H.sub.34 O.sub.8 S.sub.2 : (Monomer) Calc'd: C,70.69; 
H,3.85; S,10.89. Found: C,69.39; H,3.95; S,10.75. 
Product IV had an initial Tg of 45.degree. C., as determined by DSC 
(10.degree. C./min) and, following curing at 550.degree. F. for 8 hours, a 
cured Tg of 232.degree. C., as determined by TMA (10.degree. C./min).