5326
BKOOKEK, K E Y E S , S P R A G U E , [COMMUSICA r I O S S O .
VANDYKE, VANLARE,V A N Z A N D T
1%6 FROM THE
KOIIAK
RESEARCH LABORATORIES]
Studies in the Cyanine Dye Series. XI.’ BY
AND I V H I T E
The Merocyanines
L. G. S. BROOKER, G. H. KEYES,K. H. SPRAGUE, R. H. VANDYKE,E. F. L. WHITE
VANLARE,
G. VANZANDTAND
Llcthods of preparation are described for a large group of un-ionized dyes, called )tieyo( ycinzner, characterized by the amide ‘ I B 1 csoiiancc system, > 1;- ( C = C - ) , , C 4 +..+ > S=(C-C=),LC-O 111these new dyes the nitrogen and carbonyl “end\” of thc amide system are gcncrally iiicludcd in rings, a5 shown in the general formula
although conipounds having the carbonyl end in an open-chain system need riot be excluded from the class. The color5 of the dyes vary from almost colorless to greenish-blue; many of them are strong photographic sensitizers,
While searching for photographic sensitizing compounds, which may be cyclic or otherwise, dyes of new types it was found that p-dialkylamino- with cyclic intermediates which contribute the benzylidene derivatives of certain keto-methylene nitrogen end of the amidic chromophoric system. compounds were sensitizers.2 These dyes include, The new dyes thus formed include a number that for example, 5-(p-dimethylaminobenzylidene)-rho- are strong photographic sensitizers. 3a danine (I) (Feigl’s reagent for silver) and 2-$It is perhaps simplest to outline the nature of diethylaminobenzylidene - 3 (2H) - thianaphthenone the reactions and the products which are formed, (11). The color-conferring system common to by citing specific examples. Thus, starting with the cyclic keto-methylene compound, 3-ethyln rhodaniae , and condensing this with intermediates which contribute the benzothiazole ring, it is possible to prepare the vinylogous series of dyes, 111. Since a portion of the molecule of one of these dyes is identical with that present in a I XI cyanine, the general name “merocyanine” (pepos, these is the amidic grouping, > N--(C=C-) ,,C=O 0 , I €3 l e +--+ >N=(C-C=)&-O, and it was considered worthwhile to prepare other dyes containing this s cs LL)s/’ system, but in which the nitrogen atom formed Et 111 part of a heterocyclic ring. Many such dyes have now been prepared, and part) was suggested to us by Dr. Fraiices 11. of a wide variety of types3 In general, they may Hamer, and this name has now appeared in a be obtained by the condensation of keto-methylene number of publications. i l ) Part X, THISJOURNAL, 79, 1094 (1951). The first member of the series, I11 (Le,, n = 0), (2) L. G. S. Brooker, U. S. Patent 2,089,729 (1937); Kodak Ltd. may be obtained in good yield by the condensation British Patent 449,527 (1936). Observations in the same general field of 2-phenylmercaptobenzothiazoleethiodide with were made independently by J. D. Kendall, British Patents 428,222, 3-ethylrhodanine in alcoholic solution using tri428,380 (1935). (3) (a) L. G. S. Braoker and collaborators, U. S. Patents 2,078,233 ethylamine as condensing agent. If the benzo(1937). 2,153,169; 2,161,331; 2,165,219; 2,165,338; 2,170,803-2,170,thiazole salt in this reaction is replaced by 2(or 4)807; 2,177,401-2,177,403 (1939). 2,185,182; 2,185,343; 2,186,624; phenylmercaptopyridine ethiodide, the product 2,211,762 (1940). 2,231,659; 2,263,757 (1941). 2,282,116 (1942). is a compound such as IV, while use of 2(or 3 ) 2,341,357 (1944). 2,409,188 (1946). 2,430,558 (1947). 2,441,530; 2,454,629 (1948). 2,493,747-2,493,748; 2,494,031; 2,519,001; 2,526,632 phenylmercapto (or iodo)-quinoline ethiodide yields (1950). Kodak, Ltd., British Patents 450,958 (1936.). 466,097; a quinoline derivative such as V or VI. C o i n \\
466,244; 470,726 (1937). 493,453 (1938). 518,904 (1940). 532,088 (1941). 557,294 (1943). 577,548 (1946). 599,631; 599,636; 603,492; 606.141 (1948). 618,073; 625,446 (1949j. (b) The study of the merocyanines was well advanced in our laboratory when patents were issued ., Kendall, British Patents: 426,718: from another source [J. 1 428,222; 428,360; 428,359; 432,628 (1935)l. The present paper is a description of our entirely independent results. (c) Some merocarbocyanines derived from 3(2H)-thianaphthenone were also described by T. Ogata [Bull. I n s l . Phrs. Chctiz. Res., Tokyo. 18, 556 (1934) I but dyes of this particular subgroup had already been made by us beSore Ogata’s publication appeared. (d) G. SChwdrz has described the iudependent preparation of dyes of certain types dealt with in the present paper [Beilage Xo. I , p. 1, Phof. K o r r . , ‘79 (1937)l He apprsrh to have Considered that they offered no advantages as sensitizers u ~ r r ”weil wir diese Farbstoffe ais Sensihilisatorcii peacnutwr a n d e r c n 1 ~ e l i : ~ten ~ i n Farbstoffcn i i l ~ i i n orteiltiait ~ lirtr~clit~t 1,i11e*i * ’
0
VI
\s
cs
pounds of the latter type are also obtainable by condensing quinoline ethiodide with 3-ethylrhod-
Nov., 1951
anine in the presence of potassium hydroxide. Dyes such as the foregoing, in which the two-ring systems are linked together directly, may be called “simple merocyanines,” though chemical names have been used in the experimental section for the individual compounds. A number of cyclic keto-methylene compounds may similarly be linked with the basic nuclei of 111-VI. These include the following 0
0
0
0 3(2H)-benzofuranone
3(2H)-thianapht henonc
n
s-c
0
2-imino-4-thiazolidones
2-thio-2,4-oxazolidinediones
\CH3
0
0 RK-C
2-amino-4(5H)thiazolones
oxindoles
1,3-indandione
0
2,4-thiazolidinediones 0 R,N--(!!-S/
RS-C
I
Sd-h-
)CHg
R
2-thiohydantoins
I ‘CH, N=C/ R 5-pyrazolones
reaction is of value for the conversion of quaternary salts of heterocyclic bases containing reactive alkylmercapto, or similar negative groups, into salts containing reactive methyl, when these latter are not otherwise accessible.6 The rings which contain the nitrogen of the amidic chromophore include, besides the benzothiazole and the 2- and 4-pyridine and quinoline rings already mentioned, single-ring systems such as thiazoline, thiazole and pyrrole; condensed two-ring systems such as benzoxazole, benzoselenazole, 1-isoquinoline, pseudo-indole, benzimidazole ; condensed three-ring systems such as the benzoquinolines and the naphthoxazoles and naphthothiazoles. The next higher vinylogs of the simple merocyanines, such as I11 (n = 1) may be called “merocarbocyanines.” The first representatives of this series were prepared by Rodd and Watts,6 who treated pyrazolones containing a reactive methylene group with intermediates containing the p-anilino (or acetanilid0)-vinyl group,7 such as 2-p-acetanilidovinylbenzothiazole ethiodide (X, n = 1). However, many compounds other than pyrazolones may be employed. 3-Ethylrhodanine, for in\C-(
5(4H)-isoxa- barbituric zolones acids
2-thiobarbituric acids
Me \‘I I
MeCl IX
salt with ethyl malonate gives VIII, a type which is also of interest as a dye intermediate, for hydrolysis with boiling hydrochloric acid is accompanied by spontaneous dicarboxylation, the product being 2-methylbenzothiazole methochloride (IX). 4 This (4) L. G . S. Brooker and W. W. Williams, U. S. Patent 2,330,203 (1943).
CH=CH--),S(
COCH3 CeHa
Et1
Non-cyclic keto-methylene compounds include the following: acetylacetone, ethyl malonate, malonanilide, cyanoacetamide, cyanoacetanilide, cyanoacetophenone, ethyl cyanoacetate. Thus, condensation of 2-methylmercaptobenzothiazole metho-p-toluenesulfonate with acetylacetone gives VII, an open-chain merocyanine that is useful in further reactions (cj. XII). The condensation product of the 2-methylmercaptobenzothiazolium
Me VI11
5327
CYANINE DYE SERIES: MEROCYANINES
x
stance, condenses readily with X ( n = 1))either in acetic anhydride solution in the presence of fused sodium acetate, or in alcoholic solution in the presence of triethylamine, to give I11 (n = 1) in high yield. Hippuric and aceturic acids are open-chain ketomethylene compounds of a type that undergoes condensation in acetic anhydride with intermediates such as X ( n = 1 or 2 ) with accompanying cyclization ; the nierocarbo(or dicarbo)-cyanines that result are derivatives of 5(4H)-oxazolones (e.g., XI).809
Et
XI
Merocarbocyanines containing substituents in the dimethine bridge include a number of strong sensitizers.l” Dyes of this class, e.g., XIII, may be prepared by the condensation in acetic anhydride of a reactive keto-methylene compound with a reactive pseudo-ketone such as XII. Compounds of this latter class are commonly prepared by the action of an acid chloride upon a quaternary salt containing reactive methyl (e.g., IX) in cold pyridine suspension.11 They may also be pre( 5 ) An example is given by L. G. s. Brooker, G. H. Keyes and W. W. Williams, THISJOURNAL, 64, 199 (1942). (6) Imperial Chemical Industries, Ltd., E. H. Rodd and G. E. Watts, U. S. Patent 2,032,502 (1986); British Patent 866,964 (1032). (7) Imperial Chemical Industries, Ltd., E. H. Rodd and G. E. Watts, British Patent 344,409 (1931). (8) G . H. Keyes and I, G. S. Brooker, U. S. Patent 2,185,343 (1940). (9) See the azlactones of E. Erlenmeyer, Jr., A n n . , 276, 1 (1893); ibid., SS7, 265 (1904). (IO) L. G. S. Brooker and F.L. White, U. S. Patent 2,166,338 (1939). (11) L. G. S. Brooker and F.L. White, U. S. Patent 2,112,139 (1938).
53-3s
13ROOKER, KEYES, SPRAGUE,
VANDYKE, V.4NLLIRE, VANZANDT AND WHITE
u,,T)C=CH-CH=C(
Et
_.
Et
SI1
Vol. 73
s-csI -
XYII
0 C-NC~HISOBH
J;s\ ' S /C=CH-cH= Et
SI11
Et
pared by the acid hydrolysis of acetylacetone condensation products of the type of VII.12 In certain cases i t may be advantageous to convert the reactive pseudo-ketone (e.g., XII) into the corresponding pseudo-thioketone (e.g., XIV) l a and
f)"
+
\C=CH-CSCH, XIL
Et
xv
EtX
thence, by addition of alkyl 9-toluenesulfonate or the like, into a reactive alkylmercapto intermediate (e.g., XV), capable of condensing with a ketomethylene compound to give a chain-substituted merocarbocyanine (e.g., XIII). Still another route to these latter dyes lies through reactive chloro(or bromo)-salts such as XVI, obtainable from the pseudo-ketones (e.g., XII) by the action of phosphorus oxychloride (or oxybromide).'*
I
CHI EtCl
XVI
Merodicarbocyanines such as I11 ( n = 2) may be prepared by condensing the appropriate ketomethylene compound with acetanilidobutadienyl intermediates such as X (n = a),and the merotricarbocyanines (e.g., 111, n = 3) result from the use of intermediates with still longer conjugated chains (e.g., X, n = 3). The absorption maxima of the merocyanines vary all the way from the near ultraviolet, where the dye is almost colorless, to the near infrared, where the dye is greenish-blue. A detailed examination of the relation between absorption and structure is reserved for the following paper. The relatively low solubility of many of the merocyanine dyes in the solvents commonly used in photographic work is sometimes a disadvantage. Increased solubility has been attained by the introduction of a carboxyl or sulfonic acid group into the ketomethylene component used in making the dyes.15 Examples of dyes so obtained are XVII and XVIII. (12) (1944). (13) (1943) (14)
L. G. S Brooker and P L. White, U. S. Patent 2,341,357 L. C S
Brodrr
I,.
BrooLcr an
I I Keyez 1
S
Patent 2
I'
S
I'dtent
I
\\ tiitc,
4t'+ b47
2.2'31,65!1
(1(141)
(15) (IQiO)
L G
S Brooker and F L
I\Iiitc, U S. Patent 2,526,632
