Glutaconic aldehyde

Glutaconic aldehyde dianiiide, m synthesis of heptamethine thiazolocyanines, 57... 

Scheme 1. Principle of cyanine dye synthesis leading to trimethine (n = l), pentamethine (n = 2) and heptamethine (n = 3) chromophores. Structures comprising indolic subunits are usually named indocarbocyanine, indodicarbocyanine and indotricarbocyanine, respectively. Formic acid, malonic aldehyde, glutaconic aldehyde are used in their protected dianUide or orthoester form. They can be applied as substituted derivatives to introduce residues into the polymethine unit. The indolic substructure might bear further residues or annelated aromatic rings...

By the same token that aza substituents retard electrophilic substitution, so they accelerate nucleophilic substitution,19,20 40 41 particularly when positively charged. In an interesting study based on this type of reactivity, the equilibrium 16 = 17 has been investigated,85 and this and the rate of subsequent ring opening leading to substituted anils of glutaconic aldehyde found to correlate with o. ... 

The transformations given in our essay might have been designated essentially as a part of the chemistry of vinamidinium salts (7) and their vinylogues (8) or more simply as the chemistry of malondialdehyde and of its vinylogue glutaconic aldehyde. 

In this method, cyanide reacts with bromine water to form cyanogen bromide, CNBr, which then reacts with pyridine to yield glutaconic aldehyde. This aldehyde is condensed with an aromatic amine (benzidine) to form a red polymethine dye, which is the basis for determination of cyanide. The excess of bromine is reduced with As(III). The colour intensity reaches a maximum after 15 min, and remains constant for a further 30 min. 

The glutaconic aldehyde formed in the reaction of cyanogen bromide with pyridine has been condensed with anthranilic acid [12]. In the determination of cyanide, use has also been made of the polymethine dye which is formed in the reaction of cyanogen chloride with pyridine and barbituric acid. Chloramine T has been used for the chlorination of cyanide. This highly sensitive method (e = 1.0-10 at 580 nm) has been studied in detail [13—16]. 4-Methylpyridine has been suggested instead of pyridine [17]. 

N-(5-anllino-2,4-pentadienylidene)-aniline hydrochloride glutacon-aldehyde dianllide hydrochloride... 

Stable and has to be prepared not more than a few days before use, either by irradiating aqueous pyridine with ultraviolet light according to equation (52) or by treatment of JV-(4-pyridyl)pyridinium chloride hydrochloride with alkali according to (53). Products 53 and 54 of these reactions are enolate salts derived from glutaconic aldehyde (55), and are able to condense with primary amines in the presence of acid (equation 54)... 

Glutaconic aldehyde can react with compounds other than primary amines , for example it undergoes condensations at C-positions with pyrrole derivatives that tautomerise according to equation (51). 

A sensitive test for pyridine is based on the fact that it reacts with bromeyanogen and primary aromatic amines to give colored Schiff bases of glutaconic aldehyde. These products are known as polymethine dyes (compare Volume II, page 394). The net equation of this formation of the dyes is ... 

For the detection of phosgene in air, a filter paper impregnated with a mixture of -nitrobenzylpyridine and N-benzylaniline can be used. With 4-/>-nitrobenzylp3Tidine, the phosgene forms a derivative of glutaconic aldehyde which condenses with N-benzylaniline to give a pink to red poly-methine dye. 

Test with glutaconic aldehyde (4-pyridylpyridinium dichloride) ... 

Glutaconic aldehyde reacts with hydrazine under acid conditions to give an intensely red product. 

Though glutaconic aldehyde itself is only slightly stable, it can be easily obtained through the hydrolysis by dilute sodium hydroxide of 4-pyridyl-pyridinium dichloride which is readily available. 

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