2,4-Cyanine, synthesis

Amyl nitrite, in monomethine thiazolo-cyanine synthesis, 52 Anhydrobase. monomeric, formation of,... 

Biselenazole derivatives, synthesis, 224 Bis-o-(formylmethylamino) diphenyldi-sulfide. in trimethine thiazolo-cyanine synthesis, 42 Bis-(3-methy 1-4-phenylthiazole) mono-... 

Maionic add, in monomethine thiazolo-cyanine synthesis, 52 4-Mercaptoimidazolium hydroxide inner salts, from 5-hydroxy THISs, 11 from 5-mercaptothiazolium salts, 12 2-Mercaptoselenazoles. substituted in 4-positions, photographic emulsion, 237... 

Sodium nitrite, in monomethine thiazolo-cyanine synthesis, 52 Solvatochromism, of neutrocyanines, 75 of selenazole dyes. 251 Solvent, effect in resonance theory, 71 polarity of, in relation with solvatochromism. 75... 

A simUar phosphamethin-cyanine synthesis starting from tris-trimethylsilyl-phosphine has been described by Markl. Using this procedure, arsamethin-cyanines can also be prepared from tris-trimethylsilyl-arsin... 

X 10" M sharply decreased auxin levels. In seedlings of Amaranthus caudatus the inhibition of light-induced beta-cyanin synthesis by abscisic acid was antagonized by several phenols including coumarin (maximal effect at 10 M). ... 

In the first chapter, devoted to thiazole itself, specific emphasis has been given to the structure and mechanistic aspects of the reactivity of the molecule most of the theoretical methods and physical techniques available to date have been applied in the study of thiazole and its derivatives, and the results are discussed in detail The chapter devoted to methods of synthesis is especially detailed and traces the way for the preparation of any monocyclic thiazole derivative. Three chapters concern the non-tautomeric functional derivatives, and two are devoted to amino-, hydroxy- and mercaptothiazoles these chapters constitute the core of the book. All discussion of chemical properties is complemented by tables in which all the known derivatives are inventoried and characterized by their usual physical properties. This information should be of particular value to organic chemists in identifying natural or Synthetic thiazoles. Two brief chapters concern mesoionic thiazoles and selenazoles. Finally, an important chapter is devoted to cyanine dyes derived from thiazolium salts, completing some classical reviews on the subject and discussing recent developments in the studies of the reaction mechanisms involved in their synthesis. 

In 1923, Mills introduced thiazole for the first time in the synthesis of methine dyes through a somewhat indirect route. In order to demonstrate the 2,4 -cyanine mechanism of formation by quinoline and quinaldine quaternary salts reacting together, Mills used other pairs of quaternary salts as 2-methylthiazolium with either quinolinium or benzothiazolium (42, 43). 

These dyes possess two independent chromophoric chains of even methine (neutro) and uneven methine (cyanine) fixed on a central ketometbylene nucleus. The methylene reactive group is first used for the neutrocyanine synthesis in position 5. the, quaternization of which can ensure a subsequent polymethine synthesis in position 2 of a cationic dye by ordinary means (Scheme 58). As indicated, this quaternized neutrocyanine (37) may as well give another neutrocyanine. 

By varying the molecular stmcture, it is possible to synthesize dye initiators with the requited characteristics. The synthesis of polymethine dyes with different chain length, end groups, and substituents, or with other variations of the chromophore, has been summarized (3,4,9,21,73,74) (see also Cyanine dyes). 

General synthetic methods were developed after 1920 and extended to many new systems. Oxidative syntheses of dyes are primarily of historical interest (1), whereas nonoxidative syntheses are the most versatile and employ varied combinations of nucleophilic and electrophilic regents. One review Hsts references for the synthesis of dyes prepared before 1959 (12), and another review provides supplemental references to more recent compounds (13). Many nucleophilic and electrophilic reagents used to synthesize cyanine and related dyes are tabulated in Reference 16. 

Stmctural variations of the reagents used in these reactions have been a primary source of progress in dye synthesis. Acetylenic reagents for cyanine dye synthesis include the weU-known acetylenic quartemary salts as general electrophilic reagents for the preparation of carbocyanine dyes. A number of tautomeric pairs of acetylenic dyes have been prepared and their tautomeric equiUbria determined (dyes (26a), (26b)) (29). 

During the 1950s and 1960s Hafner used Konig salts, derived from the reaction of A -methyl aniline with Zincke salt 1, for azulene synthesis. The Zincke reaction also achieved prominence in cyanine dye synthesis and as an analytical method for nicotinamide determination. ... 

Fry et al. prepared quaternary salts from 4-methyl- and 4-methyl-thio-quinazoline and found that the same cyanine dyes were obtained by suitable reactions of either salt. An unambiguous synthesis of the 4-methylthio salt (69) from l-methylquinazoline-4-thione (70) proved that both of the salts carried groups on N-1. 

Synthesis by alkali-metal/hydrogen exchange in unsubstituted alkali-metal 9,10-phenanthreno-cyanines leads to metal-free products, e.g. 8. 

Chain-bridged cyanines, see Thiazoio-cyanines, chain-bridged Chain-bridged thiazolocyanines, see Thia-zolocyanines, chain-bridged Charge distribution, on methine chain, 72 2-Chloro-3,3-dimethylindolenine, in synthesis of pentamethine thiazolocyanines. 56... 

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