Methine dyes from tetrahydroquinoline compounds containing N-thioether substituents, in general produce bright yellow shades when applied to polyester fabrics by conventional dyeing procedures, have improved properties such as dyeability, fastness to light, resistance to sublimation, insensitivity to pH changes, and dye at the boil and under pressure to the same depth of shade. These compounds are particularly useful in the thermal fixation technique for dyeing polyester materials.

The methine dyes of this invention derived from N-substituted 
tetrahydroquinoline compounds generally produce bright yellow shades on 
polyester fabrics and have one or more improved properties such as 
dyeability, fastness to light and crock, wash resistance to sublimation, 
good Barre' coverage and leveling. The dyes generally are insensitive to 
pH changes, dye at the boil and under pressure to the same depth of shade, 
and are particularly useful in the thermal fixation technique for dyeing 
polyester materials. 
The dyes of this invention have the following generic formula: 
##STR1## 
wherein X is selected from cyano, carbamoyl, lower alkyl carbamoyl, lower 
alkoxycarbonyl, lower alkylsulfonyl and arylsulfonyl; R, R.sup.1, and 
R.sup.2 are independently selected from hydrogen and lower alkyl; R.sup.3 
is selected from hydrogen, lower alkyl, lower alkoxy, fluorine, chlorine 
and bromine, and n is 0, 1 or 2; R.sup.4 is lower alkylene; R.sup.5 is 
selected from hydroxyethyl, acyloxyethyl and substituted and unsubstituted 
phenyl, benzyl, phenylethyl, cyclohexyl, pyridyl, quinolyl and pyrimidinyl 
radicals, and azolyl radicals having the formula 
##STR2## 
wherein Y is an ethylenically-unsaturated, two-atom chain of carbon atoms 
or a nitrogen and a carbon atom, X is an oxygen or sulfur atom or when Y 
is a two-atom carbon chain of atoms X can be a nitrogen atom, and when Y 
is a chain of two nuclear carbons of a phenylene ring, said azolyl 
radicals can be benzothiazolyl, benzoxazolyl or benzimidazolyl, each of 
which may be substituted with up to two groups independently selected from 
F, Cl, Br, NO.sub.2, lower alkyl, lower alkylamino, lower alkanoylamino, 
lower alkoxy, hydroxy and cyano. The term "lower" as used herein is from 
1-8 carbons. 
The R.sup.5 phenyl, benzyl and cyclohexyl radicals may be substituted with 
such groups as lower alkyl, lower alkoxy, lower alkoxycarbonyl, lower 
alkylether, hydroxy, cyano, flourine, chlorine, bromine and nitro. Typical 
are p-chlorophenyl, m-bromophenyl, m-nitrophenyl, p-tolyl, p-anisyl, 
o,p-dichlorophenyl, p-butoxyphenyl, p-ethylphenyl, p-ethylbenzyl, 
p-methoxybenzyl, m-bromobenzyl, o,p-dichlorobenzyl, 
p-methoxycarbonylbenzyl, p-hydroxybenzyl, m-cyanobenzyl, 
3-methylcyclohexyl, 4-methylcyclohexyl and 3,3,5-trimethylcyclohexyl. The 
pyridyl, quinolyl and pyrimidinyl radicals may be substituted with lower 
alkyl, such as 4-methyl-2-pyridyl, 7-ethyl-2-quinolyl and 
4,6-dimethyl-2-pyrimidinyl. 
The --X--Y-- atoms of above R.sup.5 may complete, for example, 
##STR3## 
The carbons and any secondary nitrogen atoms of these radicals may be 
substituted, such as, 5-phenyl-1,3,4-oxazol-2-yl, 
5-acetamido-1,3,4-thiadiazol-2-yl, 6-methyl-2-benzothiazolyl, 
4,6-dichloro-2-benzothiazolyl, 6-cyano-2-benzoxazolyl, 
6-methylsulfonyl-2-benzothiazolyl, 5-methoxy-2-benzoxazolyl, 
6-nitro-2-benzothiazolyl, 2-benzimidazolyl, 6-thiocyano-2-benzothiazolyl, 
2-thiazolyl, and 4,6-di-bromo-2-benzothiazolyl. 
Preferred groups represented by R.sup.5 have the formulae 
##STR4## 
wherein R.sup.11 is hydrogen, lower alkyl, lower alkoxy, F, Cl or Br; 
R.sup.12 is hydrogen, lower alkanoylamino or lower alkylsulfonamido; 
R.sup.13 is hydrogen, lower alkyl, phenyl or phenyl substituted with lower 
alkyl, lower alkoxy, F, Cl or Br; 
R.sup.14 is hydrogen, lower alkyl, lower alkoxy, F, Cl, Br, nitro, lower 
alkylsulfonyl, cyano or thiocyanato; 
R.sup.15 is hydrogen or lower alkyl; 
X is --O--, --S-- or --NH--; and 
n' is 1 or 2; and 
n is 0, 1 or 2. 
The most preferred group of the above dyes are of the generic formula of 
page 2 wherein R, R.sup.1, R.sup.2 and R.sup.3 are individually selected 
from hydrogen and methyl, X is cyano, R.sup.4 is ethylene, and R.sup.5 is 
2-benzothiazolyl or 2-benzoxazolyl. Of these, the preferred dye is R, 
R.sup.1 and R.sup.2 as methyl, R.sup.3 as hydrogen, X as cyano, and 
R.sup.5 as 2-benzothiazolyl. This dye has particularly exceptional 
sublimation fastness, fastness to light, crock fastness, pH stability, 
build-up, leveling properties and good energy of application properties. 
These compounds are particularly distinguished from the previously known 
tetrahydroquinoline methine dyes, such as those disclosed in U.S. Pat. No. 
3,247,211 and U.S. Pat. No. 3,240,783 by improved pH stability. The 
previously known tetrahydroquinoline compounds have been limited in 
utility in the dyeing of polyester fabrics because of loss of color under 
high pH (6-8) conditions during the dyeing operation. The subject dyes are 
stable at high pH and result in full color yield and complete utilization 
of the dye even at pH levels of 8 or above. 
The quinoline compounds used as starting materials for the present dyes are 
described in Elderfield's review (R. C. Elderfield, "Heterocyclic 
Compounds," Volume 4, John Wiley and Sons, Inc., New York, New York, 
1952). Other references are J. Gagan and D. Lloyd, Chem. Communications, 
1967, pp 1043-1044, Roberts and Turner, J. Chem. Soc., 1927, 1832, 
Houben-Weyl, Volume II, Part 3, p. 326, R. M. Acheson, "An Introduction to 
the Chemistry of Heterocyclic Compounds," Interscience Publishers, Inc., 
New York, New York, 1960, Chapter VI. The reduction of the quinoline 
compounds to the 1,2,3,4-tetrahydroquinoline derivatives is a well-known 
reaction.