Hydrazone formation reagent

In certain cases this reduction (with lithium aluminum hydride) takes a different course, and olefins are formed. The effect is dependent on both the reagent concentration and the steric environment of the hydrazone. Dilute reagent and hindered hydrazone favor olefins borohydride gives the saturated hydrocarbon. The hydrogen picked up in olefin formation comes from solvent, and in full reduction one comes from hydride and the other from solvent. This was shown by deuteriation experiments with the hydrazone (150) ... 

When present in macro quantities, aldehydes and ketones can be determined by conversion to the 2,4-dinitrophenylhydrazone which can be collected and weighed. When present in smaller quantities (10 3M or less), although hydrazone formation takes place, it does not separate from methanol solution, but if alkali is added an intense red coloration develops the reagent itself only produces a slight yellow colour. Measurement of the absorbance of the red solution thus provides a method for quantitative determination. 

Cascade Blue hydrazide is soluble in aqueous solution, and it should be stable for awhile if protected from light. A concentrated stock solution of the reagent may be prepared in water and an aliquot added to a buffered reaction medium to facilitate the transfer of small quantities. For aqueous reactions, a pH range of 5-9 will result in efficient hydrazone formation. 

Hydrazinium salts, 73 567-568 2-(4-Hydrazinocarbonylphenyl)-4,5-diphenylimidazole (HCPI), chemiluminescence reagent, 5 851 Hydrazone formation, microwaves in, 76 565... 

These reagents react with carboxylic acids to form Mmc esters by heating in aprotic solvents (benzene, dioxane) at 80 °C [478, 479]. For the derivative formation of (Z-keto acids, hydrazone formation with dimethylhy-drazine and esterification with one of these reagents was suggested. 

Hydroperoxides have been obtained from the autoxidation of alkanes, aralkanes, alkenes, ketones, enols, hydrazones, aromatic amines, amides, ethers, acetals, alcohols, and organomineral compounds, eg, Grignard reagents (10,45). In autoxidations involving hydrazones, double-bond migration occurs with the formation of hydroperoxy—azo compounds via free-radical chain processes (10,59) (eq. 20). 

The most popular reagent for the formation of aldehyde and ketone derivatives is 2,4-dinitrophenylhydrazine which forms hydrazones containing strong chromophores. 

Hydrazide-containing PEG-biotinylation reagents provide reactivity with carbonyl groups (e.g., aldehydes) to label carbohydrates or glycoproteins via hydrazone bond formation (Figures 18.19 and 18.20). The hydrazide group also may be coupled with carboxylate-containing... 

Several reviews and research papers discussing the application and extension of this method have appeared.40 For example, Weber et al.41 reported an interesting result in which cerium acted as a counterion in the modified proline auxiliary (SAMEMP 40) for selective addition of organocerium reagents to hydrazones. The initial adduct was trapped with either methyl or benzyl chloro-formate to afford the stable /V-aminocarbonatc 41 (Scheme 2-24). From this example readers can see that this proline chiral auxiliary can be used not only for a-alkylation but also for nucleophilic addition, which is discussed in detail later. 

Other papers of interest in this section report transamination of camphor-3-carbothioamides with secondary cyclic amines, reaction of camphorquinone with dimethyl /S-ketoglutarate, the use of fenchone (212 X=0) in alkene formation from Grignard reagents, bromination of 2-e/itfo-6-endo-dibromobornane to yield 2,3,6-endo-tribromoborn-2-ene, and camphor-enol trimethylsilyl ether formation by quenching the reaction mixture of butyl-lithium and camphor tosyl-hydrazone with trimethylsilyl chloride. ... 

Also other reaction types have been dealt with in CHEC(1984) and CHEC-II(19%) like reduction to alcohols (e.g., sodium borohydride), Wolff Kishner reduction, nucleophilic addition via reaction with Grignard reagents or organo-lithium compounds, and formation of imine type functional groups (e.g., hydrazones). New examples are the reaction of... 

This reaction was successfully applied to various hydrazones derived from acyclic or cyclic ketones and extended to a variety of unsubstituted vinylsilanes as acceptors (trialkyl, triphenyl and alkoxy vinylsilanes). In all cases, the regioselectivity of the addition reaction was consistent with the formation of a silicon-stabilized organozinc reagent. 

Substances with low solubility in acid can interfere with the DNPH assay. Mandel-amine (methenamine man delate), an antibacterial medication, and radiopaque contrast material will form a precipitate immediately upon addition of the DNPH reagent. The color and immediacy of formation of this precipitate distinguishes it from the yellowish precipitate of a-keto acid hydrazones. It is very important to have information on patient medications prior to evaluation of the DNPH test. 

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