Hydrazine attack

Na2S-H20, THF, 68-90% yield DCC(-H20), 67-97% yield hydrazine dil. HCl, 55-95% yield. This method is used to cleave A-phthalimido penicillins hydrazine attacks an intermediate phthalisoimide instead of the aze-... 

Mechanical stirring is not strictly necessary however, severe bmnping is sometimes encountered if it is not used. Hydrazine attacks both cork and rubber. If a dropping fimnel with ground glass joint is not available, an ordinary dropping funnel may be placed at the top of the reflux condenser. 

The 3-alkylthio groups in 1,2,4-thiadiazoles are difficult to replace. Thus, 3-alkylthio-l,2,4-thia-diazoles resist the action of aniline at 100°C, ammonia at 120°C, molten urea and ammonium acetate however, hydrazine attacks 3-methylthio-l,2,4-thiadiazole (142) forming 3-amino-1,2,4-triazole (143) (Equation (21)) <65AHC(5)119>. In contrast to 3-alkylthiogroups, 5-sulfonyl groups in... 

In accordance with the general stability of alkylthio groups in heteroaromatic systems, 3-alkylthio groups in 1,2,4-thiadiazoles are not easily replaced.Thus, 3-alkylthio-1,2,4-thiadiazoles resist theaction of aniline at 100°, ammonia at 120°, or molten urea or ammonium acetate.99 On the other hand, hydrazine attacks 3-methylthio-l,2,4-thiadiazole under restrained conditions, with formation of 3-amino-... 

Hydrazine attacks indiarubber, and cork and, when boiled in aq. soln.) glass is eroded. Hydrazine hydrate and sodium develop much heat, with the expulsion of hydrogen and ammonia. When the liquid cools, a crystalline substance is formed which is soluble in water and alcohol, and which is thought to be sodium hydrazide hydroxide, N2H5ONa. The aq. soln. gives the reactions for hydrazine. T. Weich-selfelder prepared the derivatives ... 

In the reaction of hydrazine with 2-(l-alkoxyalkylidene)-l,3-dicarbonyl compounds, the 13 C NMR spectral evidence indicates that the only point of initial hydrazine attack is the carbon atom in die ethylene bond and the only observed intermediate is the corresponding enehydrazine. MNDO calculations of the electronic characteristics showed that the reaction obeys orbital control.75... 

Topaquinone (TPQ), the oxidized form of 2,4,5-trihydroxyphenylalanine (TOPA), is the cofactor of copper-containing amine oxidases. The following model compounds have been prepared in order to understand the catalytic function of TPQ the jV-pivaloyl derivative of 6-hydroxydopamine in aqueous acetonitrile [38] topaquinone hydantoin and a series of 2-hydroxy-5-alkyl-l,4-benzoquinones in anhydrous acetonitrile (o- as well as />-quinones) [39] 2-hydroxy-5-methy 1-1,4-benzoquinone in aqueous system [40] and 2,5-dihydroxy-1,4-benzoquinone [41]. Reaction of model compounds with 3-pyrrolines revealed why copper-quinopro-tein amine oxidases cannot oxidize a secondary N [42], The studies clearly showed that certain model compounds do not require the presence of Cu for benzylamine oxidation whereas TPQ does [38,40] the aminotransferase mechanism proceeds via the -quinone form [39] the 470 nm band can be ascribed to a 71-71 transition of TPQ in />-quinonic form with the C-4 hydroxyl ionized but hydrogen bonded to some residue [40] hydrazines attack at the C-5 carbonyl, forming an adduct in the azo form [41], Electrochemical characterization has been carried out for free TPQ [43],... 

Scott and co-workers729 reported a reaction between 1-amidinio-3,5-dimethylpyrazole nitrate and hydrazine. They formulated the reaction with ring opening by hydrazine attack, followed by reclosure... 

Pyran-thiones, when treated with hydrazine, can give pyridazines, l-amino-4(l//)-pyridinethiones, or pyrazoles. Pyridazines are the exclusive or main product when the starting pyranthiones are substituted at position 3 with a hydroxy group. Perhaps hydrazine attacks position 6, followed by elimination of hydrogen sulfide to give 51 (78BCJI79). 

Now heating is stopped, and as soon as boiling ceases, the condenser is removed, and the flask is rigged for simple distillation as shown in Figure 3 in Chapter 3. The stillhead should have a thermometer in it reaching down into the middle of the liquid mass in the flask. A cork or rubber holder for this thermometer is unacceptable because hydrazine attacks these materials. The holder must be made of all glass. 

Treatment of the N-cyano-imidates (257) with o-hydrazinobenzoic acid gives triazolo[l,5-a]quinazolines (258). The hydrazine attacks the imidate carbon initially, rather than the nitrile group this contrasts with the preferential reaction at the nitrile function of the similar A -cyano-amidines (221) by amines (see p. 253) (Scheme 103). ... 

C Suppression of hydrazine attack on T with NaCl (2 M) followed by piperidine cleavage of the chain at C C... 

The synthesis of pyrazoles is somewhat related to the synthesis of pyrroles. When 2,4-pentanedione (117) reacts with hydrazine (NH2NH2) in the presence of a base such as hydroxide, the product is 3,5-dimethylpyrazole, 120. In Chapter 18 (Section 18.7.3), hydrazine reacted with ketones and aldehydes in a manner similar to amines to form imine products called hydrazones. When hydrazine attacks one carbonyl group in 117, the product is 118, and the second -NH2 unit attacks the second carbonyl to give 119. Loss of water and a sigma-tropic rearrangement gives the aromatic product, 120. This modification of the pyrrole synthesis uses hydrazine (with two -NH2 units) in the presence of a dicarbonyl compound to generate the pyrazole. 

---