Heterocyclic Hydrazines

Fused ring tetrazoles such as 96 are obtained from the reaction of nitrous acid with heterocyclic hydrazines (95) (Eq. 19).159 160 This method is also suitable for the preparation of fused ring ditetrazoles such as... 

Diazatrimethine dyes have been prepared by oxidative coupling of a heterocyclic hydrazine with an active methylenic heterocycle as in the yellow dye (31). Alternatively they may be prepared by diazotization of an aromatic or heteroaromatic amine followed... 

Systems based on the reaction of iron salts with heterocyclic hydrazines and on the oxidative coupling of 2-aminothiazoles with naphthols have also been used (64USP3129109). In a similar process a heterocyclic hydrazone, such as the benzothiazole (174), is cleaved in the presence of an oxidizing agent, and the resulting oxidation products react immediately to give an azo dye (175) (62USP3076721). 

An inorganic photoconductor such as zinc oxide can be optically sensitized by treating it with a ligand that will form a colored zinc complex. The resulting material then responds to light of the wavelength where the complex absorbs. Suitable ligands are prepared by the condensation of heterocyclic hydrazines and heterocyclic aldehydes.235 Two examples of the more than 50 disclosed in the patent literature are (114) and (115). 

The many routes used to synthesize this system have been reviewed <86AHC(39)ll7>. Since the late 1980s, emphasis has been placed on the synthesis of TV-amino derivatives both for the production of the reactive species pyrimidyne and polynitrogen heterocycles. Hydrazine insertion into the triazoles (136) (Equation (16)) produces the 6-amino derivatives (105) <88LA1107> whilst diazotization of the aminohydrazino pyrimidine (137) (Equation (17)) forms the 3-amino derivative (138) (87JHC705). 

The procedure given has been applied with varying success to a number of aromatic and heterocyclic hydrazines. ... 

Purine derivatives have also been formed by the reaction of phosgene with heterocyclic hydrazine derivatives [1161b] ... 

X-alkyl-X-arylhydrazin.es39,40 43,95-99 or heterocyclic hydrazines 93,100-108 or with semicarbazide83 and thiosemicarbazide.109 Arylhydrazincs have been extensively used for the characterization and identification of saccharides, in contrast, alkylhydrazincs have been seldom used because the alkylhy-drazon.es formed are difficult to crystallize and possess unfavorable equilibrium constants for their formation. 

The 3-j3-D-arabinofuranosyl pyrazole derivative (33) has been synthesized from D-mannose by the procedure outlined in Scheme 9 on deprotection with ammonia, (33) epimerized to the -D-ribofuranosyl isomer. 2,5-Anhydro-D-allonic acid derivatives have been used to synthesize the C- ym-triazoloribo-nucleosides (34) and (35) by condensation with heterocyclic hydrazine derivatives. The diazoketone (36), prepared conventionally from the acid, has been used to prepare the thiazole analogue (37) of ribavirin via the intermediate a-bromomethyl ketone (38) by condensation with an imido-thio-oxalic acid derivative,and the indazole nucleoside analogue (39) by cyclization with benzyne (Scheme 10). An acyclic diazoketone analogously prepared from D-ribonic acid similarly gave a C-ribonyl-indazole with benzyne, which could be... 

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