Hydrazone

About: Hydrazone is a research topic. Over the lifetime, 4853 publications have been published within this topic receiving 65160 citations. The topic is also known as: hydrazone.

Fluorinated heterocyclic compounds. An effective strategy for the synthesis of fluorinated Z-oximes of 3-perfluoroalkyl-6-phenyl-2h-1,2,4-triazin-5-ones via a ring-enlargement reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles and hydrazine.

Abstract: The reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of the hydrazine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring opening and ring closure with enlargement, leads with high yield and in very mild experimental conditions to the formation of Z-oximes of 3-perfluoroalkyl-6-phenyl-2H-1,2,4-triazin-5-ones (11a−c) as major products of the reaction. In turn, the hydrazine can attack the electrophilic carbonyl carbon giving 4-perfluoroacylamino-5-phenyl-2H-1,2,3-triazoles (13a−c) through the well-known Boulton−Katritzky rearrangement of the intermediate hydrazones.

Chemische synthese verzweigter polysaccharide, 5. Kopplung von oligosacchariden und amylose an verschiedene träger durch hydrazonbindung

Abstract: The coupling of glucose and maltooligomers by hydrazone linkage to carriers by means of acid hydrazide groups was investigated. The following carriers were used: (1) linear polymers such as (a) poly(ethylene glycol) with carboxymethyl (CM) end groups, (b) CM-amylose and CM-cellulose, 6-COOH amylose and 6-COOH cellulose, pectic acid, alginic acid, poly(acrylic acid); (2) multifunctional centers such as (c) CM-cyclodextrin, 1,3,5-benzenetricarboxylic acid, 1,3,4,5-benzenetetracarboxylic acid, crosslinked poly(acrylamide) (BIO-GEL). The hydrazone linkage which is formed preferably in borate buffer at pH 8,5 was stable above pH 6 and could be split by mild acid treatment at pH 4. Maltooligomeric grafts of degree of polymerization DP ≧ 4 may be extended enzymatically by phosphorolytic synthesis to amylose chains of variable length. Primer activity of the bound maltooligomers for phosphorylase was obviously not hindered by the hydrazone linkage, by free hydrazide groups, or by synthetic polymers as carriers. ABA-Block copolymers may be derived from(a), comb-like molecules from (b), and different kinds of star-like molecules from (c).

Synthesis and antibacterial evaluation of novel heterocyclic compounds containing a sulfonamido moiety.

Abstract: Aiming for the synthesis of new heterocyclic compounds containing a sulfonamido moiety suitable for use as antibacterial agents, the precursor ethyl {[4-N-(4,6-dimethylpyrimidin-2-yl)sulfamoyl]phenylazo}cyanoacetate was reacted with a variety of active methylene compounds producing pyran, pyridine and pyridazine derivatives. Also, the reactivity of the precursor hydrazone towards hydrazine derivatives to give pyrazole and oxazole derivatives was studied. On the other hand, treatment of the same precursor with urea, thiourea and/or guanidine hydrochloride furnished pyrimidine and thiazine derivatives, respectively. The newly synthesized compounds were tested for antibacterial activity, whereby eight compounds were found to have high activities.

Controlled Release of Volatile Aldehydes and Ketones from Dynamic Mixtures Generated by Reversible Hydrazone Formation

Abstract: Delivery systems generated by reversible hydrazone formation from hydrazine derivatives (see Fig. 1) and carbonyl compounds in H2O efficiently increase the long-lastingness of volatile aldehydes and ketones (R1R2CO) in various perfumery applications. The hydrazones are usually obtained in an (E) configuration at the imine double bond (NHNC) and, in the case of aliphatic acylhydrazones R′CONHNCR1R2 (R′=alkyl), as syn and anti conformers with respect to the amide bond (CONHN). An average free-energy barrier of ca. 78 kJ/mol was determined for the amide-bond rotation by variable-temperature 1H-NMR measurements (Fig. 2). In the presence of H2O, the hydrazone formation is entirely reversible, reaching an equilibrium composed of the hydrazine derivative, the carbonyl compound, and the corresponding hydrazone. Kinetic measurements carried out by UV/VIS spectroscopy showed that the same equilibrium was reached for the formation and hydrolysis of the hydrazone. Rate constants are strongly pH-dependent and increase with decreasing pH (Table 1). The influence of the hydrazine structure on the rate constants is less pronounced than the pH effect, and the presence of surfactants reduces the rate of equilibration (Tables 1 and 3). The full reversibility of the hydrazone formation allows to prepare dynamic mixtures by simple addition of a hydrazine derivative to several carbonyl compounds. Dynamic headspace analysis on dry cotton showed that the presence of a hydrazine derivative significantly increased the headspace concentrations of the different carbonyl compounds as compared to the reference sample without hydrazine (Table 4). The release of the volatiles was found to be efficient for fragrances with high vapor pressures and low H2O solubility. Furthermore, a special long-lasting effect was obtained for the release of ketones. The simplicity of generating dynamic mixtures combined with the high efficiency for the release of volatiles makes these systems particularly interesting for practical applications and will certainly influence the development of delivery systems in other areas such as the pharmaceutical or agrochemical industry.