Amino groups hydrazones

Oxidative Couplings of Heterocyclic Hydrazones. This method has opened the way to the preparation of azo derivatives of diazo compounds unobtainable by other means, ie, heterocycHc compounds ia which the diazotizable amino group is conjugated with the heterocycHc nitrogen atom as ia 2- and 4-amiQopyridine, compounds which do not normally yield stable diazonium salts (38). The reaction occurs as illustrated by equation 7 for the iateraction of (A/-methylcarbostyryl)hydrazone [28219-37-6] and dimethyl aniline the overall process is oxidation. 

Reaction of 2,3-dichlorobenzoyl chloride with cyanide ion leads to the corresponding benzoyl cyanide (141). Condensation of that reactive intermediate with aminoguanidine 142 leads to the hydrazone-like product 143. Treatment with base results in addition of one of the guanidine amino groups to the nitrile function and formation of the 1,2,4-triazine ring. The product, lamo-trigine (144), is described as an anticonvulsant agent [31]. 

The vast majority of azo dyes are azo compounds containing hydroxy or amino groups in the 2- or 4-position with respect to the azo group (e.g., 1.8). They are in equilibrium with their tautomers, the quinone hydrazones (quinone monoimine hydrazones). In spite of the fact that in most hydroxyazo dyes the equilibrium is shifted in favor of the quinone hydrazone, they are still called azo compounds. 

Treatment of carboxyaldehydes 252 with hydrazine hydrate in ethanolic KOH under refluxing conditions provides an easy entry to the novel imidazo[2,l-4][l,3]thiazole fused diazepinones 253 via lactone ring opening by intramolecular nucleophilic attack of the amino group of the intermediate hydrazone which could not be isolated (Equation 31) <2006TL2811>. 

As illustrated in Scheme 1, hydrazide and aminooxy groups readily form stable hydrazone and oxime bonds, respectively, with aldehydes at pH values between 3 and 5.5. The Cys 1-amino-2-thiol moiety forms a stable thiazolidine ring with the aldehyde between pH 4 and 5, whereas at these pH values an amino group, if it reacts at all, gives a readily reversible Schiff base. 

Having the electrophile 95 to hand, the synthesis proceeded by metallation of the SAMP hydrazone 96 followed by alkylation with the iodide affording the a-alkylated hydrazone 97 with diastereomeric excess de = 9S% (Scheme 1.2.21). The removal of the auxiliary proceeded smoothly with oxalic acid, leading to 98 in good yield (80%, two steps) and no epimerization without deprotection of the amino group. 

The (TV-aminoamide) link 4 is a convenient intermediate to cyclization of the peptide chain as in the cyclic initiators 81 (n=l, 2) of an a-helix (Scheme 24)J981 Replacement of the N—H O=C hydrogen bond by the N-N=CH-C hydrazone moiety gives another a-helix initiator 82, synthesized by coupling the TV-amino group with an aldehyde carbonyl/99 ... 

To expand the utility of the hydrogen bond mimic, J (23) has been modified to allow for extension from the N-terminus of a hydrazone-linked cyclic peptide 148 This allows not only the use of the hydrogen bond mimic in preparing internal loops, but also the positioning of a helix nucleation site between two peptides to form supersecondary structures. To accomplish this, an a-amino group can be added to J to give J (26) (Scheme 14). Incorporation of linker J into a nucleation site using the procedure applied to 23 allows it to mimic an N-cap formed... 

Simpler insertion reactions have been demonstrated in the case of coordinated hydrazines and hydrazones, where the terminal amino group is still nucleophilic (equation 58).J99 200... 

Lehn synthesised guanidinium-based cationic steroids incorporating an acylhy-drazone linker using the approach shown in Fig. 9 [141]. The synthesis was developed from a polyamine scaffold by guanidination of the primary amino groups and alkylation of the secondary amine with methyl chloroacetate to introduce the ester moiety required to form a hydrazide group by reaction with hydrazine monohydrate. Cationic steroid hydrazones were then prepared via an acetic acid catalysed reaction with cholestanones, which demonstrated high transfection efficiency and low toxicity in a variety of cell lines [141]. 

Hydrazone Dyes If the diazonium salts of aromatic amines are coupled with the methylene derivatives of N heterocycles, hydrazone dyes (i.e., the monoaza derivatives of the enamine dyes) are obtained. Paper and leather can be dyed in yellow to red shades with these dyes [23], They are moderately lightfast on polyacrylonitrile. If the diazo components contain substituents in the 2-position relative to the amino group that can form a hydrogen bond (e.g., 2-nitroaniline [24] or 1-ami-noanthraquinone [25]), lightfastness is improved considerably (10). 

Type I hydrazones can be described as a bis-chromophoric system D-A -D -A where A is equal to the azomethine double bond (C=N) and D is equal to the central amino group which suggests lower values of /3 in comparison to type II hydrazones (see below). Also, one expects increasing values of y with increasing... 

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