Imino linking groups

These are reddish blue 1 1 copper-complex monoazo dyes derived from a 2-naphthylamine-or 2-aminonaphtholsulphonate as diazo component and another aminonaphtholsulphonate as coupler. Often such dyes are more easily prepared using a 2-naphthylaminesulphonate and oxidatively coppering the resulting monoazo dye (section 5.5.3). In orthodox structures the imino link of H acid carries the reactive system (7.99), but in other instances the naphthylamine diazo component provides the site of attachment of a haloheterocyclic (7.100) or sulphatoethylsulphone (7.101) grouping. 

The group at Isis Pharmaceuticals have reported further on their methylene-imino-linked dimers (see Vol. 26, p. 242) and, significantly, have extended their work to the preparation of 2 -0-methylated diribonucleotide analogues 226 by linking units of type 224 and 225 under radical conditions. The compounds of type 226 could also be AT-methylated. ... 

Dicyandiamide (see p. 168) and its derivatives cross-link at 180° C by reaction of the amino and imino (=NH) groups with the epoxy ring ... 

Examples of cyclic units are 1,4-phenylene, 2,6-naphthalene and fr s-1,4-cyclohexylene rings. The linking group connects the cyclic units on each side to give the chain a linear character. The preferred confirmation is planar (linear). A number of different groups fulfil these requirements direct bond, ester, imino, azo, azoxy, and methylol groups (semiflexible). 

It may further be pointed out that there is a contradiction between Russell and Pauling (1939) (56) and Coryell and Pauling (1940) (22). The former attributed the heme-linked group, pK 9.5, in imidazole hemiglobin to the titration of the imino group (see formula A). Coryell and Pauling,... 

Many of the premetallised direct dyes are symmetrical structures in the form of bis-1 1 complexes with two copper(II) ions per disazo dye molecule. Scheme 5.12 illustrates conversion of the important unmetallised royal blue Cl Direct Blue 15 (5.43), derived from tetrazotised dianisidine coupled with two moles of H acid, to its much greener copper-complex Blue 218 (5.44) with demethylation of the methoxy groups as described above. Important symmetrical red disazo structures of high light fastness, such as Cl Direct Red 83 (5.45), contain two J acid residues linked via their imino groups. Unsymmetrical disazo blues derived from dianisidine often contain a J acid residue as one ligand and a different coupler as the other, such as Oxy Koch acid in Cl Direct Blue 77 (5.46), for example. 

Bluish red reactive dyes are almost totally dominated by H acid as the indispensable coupling component. Various mono- or disulphonated anilines or naphthylamines are suitable diazo components, but the outstandingly important one is orthanilic acid (7.96). As with orange and scarlet dyes, haloheterocyclic (Z) reactive systems are linked via the imino group of the H acid residue but sulphatoethylsulphone substituents are found in the diazo component with N-acetyl H acid as the typical coupler. A characteristic problem associated with reactive dyes derived from H acid is their accelerated fading under the simultaneous influence of perspiration and light (section 3.3.4). 

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