Aromatic amine derivatives of 2,5-dimercapto-1,3,4,-thiadiazoles

Disclosed are novel compounds prepared by reacting 2,5-dimercapto-1,3,4-thiadiazole, aliphatic or aromatic aldehyde and aromatic amine in the molar ratio of 1:1:1 to 2:4:3. The 2,5-dimercapto-1,3,4-thiadiazole may be substituted in the 2-position by hydrocarbyl, terpene, polymeric and succinate residues. The compounds possess antiwear and antioxidant characteristics.

BACKGROUND OF THE INVENTION 
The present invention concerns aromatic amine derivatives of thiadiazole 
compounds. More particularly, the thiadiazoles are derived from 
2,5-dimercapto-1,3,4-thiadiazole, an aldehyde and an aromatic amine 
compound. 
U.S. Pat. No. 2,765,289 teaches reaction products of 
2,5-dimercapto-1,3,4-thiadiazoles, aldehyde and diarylamine having an 
aldehyde-carbon to nitrogen bond. The products possess corrosion 
inhibiting properties. 
U.S. Pat. No. 4,990,273 discloses similar reaction products having extreme 
pressure and antiwear properties. 
U.S. Pat. No. 5,147,569 discloses reaction products of glycidyl 
methacrylate grafted polyolefinic epoxide and 1,3,4-thiadiazole containing 
a substituted diarylamine or a substituted phenothiazine. The compounds 
function as viscosity index improvers, antioxidants and antiwear agents. 
An object of the invention is to provide novel reaction products of 
2,5-dimercapto-1,3,4-thiadiazole, aldehyde and certain aromatic amines 
having the aldehyde-carbon bonded to the aromatic ring instead to the 
nitrogens. Another object is to provide products having antiwear and 
antioxidant properties when incorporated into lubricating compositions. 
SUMMARY OF THE INVENTION 
In accordance with the invention, there are provided novel 
1,3,4-thiadiazole compounds characterized by the structural formulae 
##STR1## 
wherein x=1-2, R represents the group 
##STR2## 
alkyl, cycloalkyl, aralkyl, terpene residue, and a succinate residue of 
the formula R.sup.1 represents hydrogen, C.sub.1-17 -alkyl, phenyl and 
phenyl substituted by alkyl groups; A represents aromatic ring structure 
selected from the group consisting of N'-phenyl-p-phenylenediamine, 
diphenylamine, naphthylamine, quinoline, hydrated quinoline, 
phenothiazine, and phenyl-(1 or 2)-naphthylamine and wherein the aromatic 
ring and amine groups may be substituted by alkyl groups; R.sup.2 
represents hydrogen, alkyl and cycloalkyl groups; and R.sup.3 represents 
the group R and a polymeric alpha-olefin residue which contains 20 to 100 
carbon atoms and is unsubstituted or has a substituent hydroxy group in 
the 2 position. 
FIG. 1 shows the infrared spectrum of the present reaction product of 
2-(1,2-di(2-ethylhexoxycarbonyl)ethylthio)-1,3,4-thiadiazole, 
paraformaldehyde and phenyl-1-naphthylamine and further described in 
Example 2 hereinbelow. 
The absorption in the region of 3324 to 3392 cm.sup.-1 indicates N--H bond 
absorption. 
DESCRIPTION OF SPECIFIC EMBODIMENTS 
The novel compounds of the invention may be prepared by reacting 
2,5-dimercapto-1,3,4-thiadiazole, aldehyde and an aromatic amine by an 
alkylation process. Preferred are reaction products wherein the 
thiadiazole, aldehyde and aromatic amine ranges in the molar ratio of 
1:1:1 to 2:4:3. 
The reaction is essentially an alkylation process wherein the 
2,5-dimercapto-1,3,4-thiadiazole and aldehyde form a hydroxy-intermediate 
which attaches to a carbon atom on the aromatic ring of the amine. The 
position of attachment to the ring may vary and mixtures may be formed. 
The products are characterized by aromatic amine N-H bond stretching 
absorption in the region of 3175 to 3450 cm.sup.-1. 
The reaction may be conducted in the presence or absence of a suitable 
inert solvent, such as toluene, dimethyl ether and others. Optionally, the 
reaction may employ acid catalysts. For example, a Lewis acid catalyst 
such as methanesulfonic acid may be used. 
An alternate alkylation process may be employed wherein a Lewis acid is 
used as a blocking agent for the aromatic amine group. A particularly 
preferred Lewis acid is acetyl chloride. The blocked amine is reacted with 
2,5-dimercapto-1,3,4-thiadiazole compound and aldehyde to form an 
intermediate product. The intermediate is hydrolyzed with a strong base 
and the product is isolated. In some cases, a weak Lewis acid, e.g. 
AlCl.sub.3 can be eliminated by addition of water. The reaction is 
conducted in the presence of solvents such as dioxane, hexane, and similar 
inert organic solvents. In the case of bicyclic aromatic amines, the 
alkylation process using the blocking agent produces higher yields of the 
alkylated product. 
The aldehyde reactant may be a normal or branched chain aliphatic aldehyde 
containing 1 to 18 carbon atoms or an aromatic aldehyde. Examples of 
suitable aldehydes include, among others, formaldehyde, acetaldehyde, 
benzaldehyde, 2-ethylhexyl aldehyde, butyraldehyde, caprylic aldehyde, 
phenylacetaldehyde, and salicylaldehyde. 
The aromatic amine may be selected from aromatic monoamines and diamines. 
The aromatic compounds may be substituted by alkyl groups on the amine 
group and the aromatic ring. The alkyl groups may be normal or branched 
chain. Particularly preferred are alkyl groups having 1 to 18 carbon 
atoms. Specific compounds include, among others, diphenylamine, alkylated 
diphenylamine such as 4,4'-dioctylphenylenediamine, phenylenediamine, 
alkylated phenylenediamine, N,N'-dioctylphenylenediamine, 
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, phenothiazine, 
phenyl-1-naphthylamine, phenyl-2-naphthylamine, 
1,2-dihydro-2,2,4-trimethylquinoline and its polymers. 
The novel 1,3,4-thiadiazole derivatives may be substituted in the 
5-position by alkyl, cycloalkyl, aryl and aralkyl groups, terpene 
residues, polymeric alpha-olefin residues and succinate residues. The 
alkyl groups may be straight or branched chain and may contain up to 100 
carbon atoms. Representative alkyl groups, among others, include methyl, 
butyl, 2-ethylhexyl, dodecyl, and octadecyl groups. Exemplary cycloalkyl 
groups include cyclopentyl, cyclohexyl and cycloheptyl. Preferred aryl 
groups are phenyl, naphthyl, phenothiazinyl and quinolyl groups. 
Particularly preferred terpene residues are pinene residue of the formula 
##STR3## 
and limonene residue of the formula 
##STR4## 
The polymeric alpha-olefin residue is essentially a hydrocarbyl radical 
having 20 to 200 carbon atoms. Typically, the molecular weight of the 
polymeric residue ranges from 280 to 2600 and higher. Preferred are 
polymers having olefinic unsaturation. The polymers may have straight or 
branched chain aliphatic units having 2 to 10 carbon atoms. Especially 
useful are polymers and copolymers of alpha-olefins as for example 
isoprene, isobutene, 2-methyl-1-heptene, ethylene, propylene, and 
2-methyl-5-propylhexene. The polymeric residue may be derived from a 
hydrocarbon polymer with an epoxide or chlorine functionality. Activated 
polyolefins are available commercially. Activated polyisobutenes with 
epoxide functionality are marketed under the trade name ACTIPOL.TM. by 
Amoco Chemical Company. Alternately, commercial polyolefins may be 
epoxidized by known methods. 
The succinate residue in the above formulae may be derived from maleic 
anhydride or acid and further esterified with normal and branched chain 
alkyl groups containing 1 to 22 carbon atoms and cyclic aliphatic groups 
such as cyclohexyl, cyclopentyl and cycloheptyl. 
The thiadiazole derivatives of the invention are useful as additives for 
lubricants. The compounds possess multifunctional properties. In addition 
to being effective antiwear agents, they also perform oxidation inhibiting 
functions. 
The amount of the thiadiazole additive required to be effective for 
imparting antiwear and antioxidant characteristics to lubricating 
compositions may range from about 0.01 to 15.0 percent of the lubricating 
composition. The preferred range is about 0.1 to 5.0 percent of the 
additive based on the weight of the lubricating composition. 
The base oil of the lubricants may be selected from naphthenic, aromatic, 
paraffinic, mineral and synthetic oils. The synthetic oils may be selected 
from, among others, alkylene polymers, polysiloxanes, carboxylic acid 
esters and polyglycol ethers. 
The lubricating compositions may contain the necessary ingredients to 
formulate the composition, as for example emulsifiers, dispersants and 
viscosity improvers. Greases may be prepared by adding thickeners, as for 
example, salts and complexes of fatty acids, polyurea compounds, clays and 
quaternary ammonium bentonite complexes. Depending on the intended use of 
the lubricant, other functional additives may be added to enhance a 
particular property of the lubricant. The lubricating compositions may 
further contain extreme pressure agents, metal passivators, rust 
inhibitors, dispersants and other known antioxidants and antiwear agents.

The following examples are given for the purpose of further illustrating 
the invention. All percentages and parts are based on weight unless 
otherwise indicated. 
EXAMPLE 1 
2-Pinanyl-5-(4,4'-dioctylphenylamino-(o or 
m)-phenylene)methylenethio-1,3,4-thiadiazole 
A reactor was charged with alpha-pinene, 49.0 g (0.36 moles), 
2,5-dimercapto-1,3,4-thiadiazole, 53.3 g (0.36 moles) and toluene, 50 ml. 
The reaction mixture was cautiously heated to 130.degree.-140.degree. C., 
followed by addition of 91% paraformaldehyde, 12.2 g (0.37 moles). After 
heating for one hour, the reactor was charged with 
p,p'-dioctyldiphenylamine, 141.5 g (0.36 moles) and toluene, 50 ml. Water 
was azeotroped off at about 135.degree. C. The product was stripped and 
filtered. 
EXAMPLE 2 
Reaction product of 
2-(1,2-di(2-ethylhexoxycarbonyl)ethylthio)-1,3,4-thiadiazole, 
paraformaldehyde and phenyl-1-naphthylamine. 
A reactor was charged with 
2-(1,2-di(2-ethylhexoxycarbonyl)ethylthio)-1,3,4-thiadiazole, 1400 g and 
91% paraformaldehyde, 110 g and heated at about 130.degree.-135.degree. C. 
for about 0.5 hours. The intermediate, 160.4 g and phenyl-1-naphthylamine, 
69.2 g and toluene, 100 ml was added and water was azeotroped off at about 
135.degree. C. The product was stripped and filtered. Infrared spectrum 
presented in FIG. 1 showed good N--H bond absorption in the region of 3324 
to 3392 cm.sup.-1. 
EXAMPLE 3 
Reaction product of 2-pinanyl-1,3,4-thiadiazole-5-thiol, isobutyraldehyde 
and diphenylamine 
A reactor was charged with alpha-pinene, 75 g, 
2,5-dimercapto-1,3,4-thiadiazole, 75 g and rinsed with acetone, 3 ml. The 
reaction was heated cautiously to 130.degree.-135.degree. C. for 5 
minutes. The reaction was stripped of excess pinene and acetone with 
aspirator under reduced pressure. After cooling to 50.degree. C., the 
reaction was charged with isobutyraldehyde, 40 g and diphenylamine, 83.5 
g. The reactor was fitted with Dean Stark attachment filled with hexane 
and heated to 130.degree. C. After collecting water, the hexane volume was 
adjusted for a reflux at 130.degree. C. and the reaction was azeotroped 
for 8 hours. The product was stripped and filtered. 
EXAMPLE 4 
Reaction product of 2-hydroxymethylthio-1,3,4-thiadiazole-5-thiol and 
diphenylamine 
A reactor was charged with 2,5-dimercapto-1,3,4-thiadiazole, 30 g, and 100 
ml dioxane and mixed. After addition of 37% formaldehyde, 16.3 g, water 
was azeotroped with hexane. Diphenylamine, 33.85 g, was added and the 
mixture was heated to azeotrope water. After cooling to room temperature, 
the mixture was dried over magnesium sulfate, filtered and the solvent was 
stripped off under vacuum at 110.degree. to 115.degree. C. 
EXAMPLE 5 
Reaction product of p,p'-dinonyldiphenylamine, formaldehyde, and 
2-mercapto-1,3,4-thiadiazole monosulfide dimer was prepared by the 
blocking method 
A reactor fitted with a reflux condenser was charged with 
p,p'-dinonyldiphenylamine, 100.3 g, and acetyl chloride, 30.0 g. The 
reaction was heated to reflux for 0.5 hour and then stripped of HCl and 
excess acetyl chloride by applying vacuum. After cooling, the reaction was 
charged with 2-mercapto-1,3,4-thiadiazole monosulfide dimer, 32.5 g, 
dioxane, 150 ml, 37 percent formaldehyde, 20.0 g, and hexane, 25 ml. The 
reaction was fitted with a Dean Stark trap filled with 25 ml hexane. The 
reaction was brought to reflux and water was azetroped until none was 
evolved. 
The intermediate product was stripped of solvents by applying vacuum. The 
intermediate was filtered by diluting with ether and tetrahydrofuran. The 
intermediate was then hydrolyzed by charging 25 g of 50 percent sodium 
hydroxide solution and refluxing for 2 hours. The hydrolyzed product was 
isolated by extraction into ether from water. The ether layer was dried 
over magnesium sulfate, filtered, and stripped to afford the product. 
For comparison, the same procedure was conducted without the blocking step. 
Both methods of alkylation demonstrated infrared absorption in the region 
of the N-H bond stretching. The reaction conducted without the blocking 
step yielded lower ring alkylation. In the case of the blocked material, 
the ring alkylation was estimated to be complete. 
EXAMPLE 6 
Thin Film Oxygen Uptake Test 
A test was conducted essentially according to the method described by 
Chia-Soon Ku et al, J. Am. Soc. Lubricating Eng., 40, 2,75-83, 1984. The 
oxidation induction time of the lubricant was measured under conditions 
which simulate the high temperature oxidation process in automotive 
engines by a modified rotary bomb oxidation test method ASTM D-2272. The 
test was conducted with 1.5 gram samples of SAE 30, motor oil. The oil was 
fully formulated with the exception of the antioxidant additive. The test 
was conducted at 160.degree. C. and initial oxygen pressure of 620.6 kPa 
(90 psi). A "pass" oil has a high induction time, while a "fail" oil has a 
low induction time. Compounds of the invention were added to the oil in 
the amount indicated in Table I. The data indicate that the additives of 
the invention have good antioxidant properties. 
EXAMPLE 7 
Modified Falex Wear Test 
A laboratory test was conducted by using the original Falex machine to 
simulate the valve train wear of an automobile engine. The V-blocks and 
pin were washed in mineral spirits with an ultrasonic cleaner, rinsed with 
acetone, air-dried and weighed. The test sample (60 g) was placed into the 
oil cup. The motor was switched on and the loading arm was placed on the 
ratchet wheel. Upon reaching the reference load of 227 kg, the ratchet 
wheel was disengaged and the load was maintained constant for 3.5 hours. 
Thereafter, the motor was switched off. The V-blocks and pin were washed, 
dried and weighed. The weight loss, a measure of wear, was recorded and 
compiled in Table II. 
The test samples were prepared by adding the compounds of the invention to 
the base motor oil (SAE 30, SF) in the amount given in Table II. The base 
oil contained 0.11 percent phosphorus and no supplemental antioxidant. The 
results indicate that the present compounds afford good antiwear 
properties. 
TABLE I 
______________________________________ 
Thin Film Oxygen Uptake Test 
Average Induction 
Sample 
Antioxidant Additive 
Percent Time, min. 
______________________________________ 
1 -- -- 108 
2 Compound of Example 3 
0.35 154 
3 2-(1,2-di(2-ethylhexoxy- 
carbonyl)-ethylthio)-5- 
(4,4'-dioctylphen- 
ylamino-(o or m)- 
phenylene)-methy- 
lenethio-1,3,4- 
thiadiazole 
4 2-(1,2-di(2-ethylhexoxy- 
0.35 138 
carbonyl)-ethylthio)-5- 
(4-phenylamino-p- 
phenylene)-methylene- 
thio-1,3,4-thiadiazole 
______________________________________ 
TABLE II 
______________________________________ 
Falex Wear Test 
Total Weight 
Sample 
Antiwear Additive Percent Loss, mg 
______________________________________ 
5 -- -- 57.2 
6 2-(1,2-di(2-ethylhexoxycar- 
0.35 3.4 
bonyl)ethylthio)-5-(4,4'- 
dioctylphenylamino-(o or m)- 
phenylene)-methylenethio- 
1,3,4-thiadiazole 
7 2-(1,2-di(2-ethylhexoxy- 
0.35 22.0 
carbonyl)-ethylthio)-5- 
(4-phenylamino-p-phenylene)- 
methylenethio-1,3,4- 
thiadiazole 
______________________________________ 
The above embodiments have shown various aspects of the present invention. 
Other variations will be evident to those skilled in the art and such 
modifications are intended to be within the scope of the invention as 
defined by the appended claims.