Hydrazines, aryl

The synthesis is often carried out by subjecting an equimolar mixture of the aryl hydrazine and aldehyde or ketone directly to the indolization conditions without isolation... 

The reaction conditions (neutral, acidic or basic) do have an affect on the regioselectivity of the reaction. Acidic reaction conditions have also been shown to preferentially provide one regioisomer over basic conditions for reactions of aryl hydrazines. Extensive studies with 2-perfluoroacylcycloalkanones and mono-substituted hydrazines were studied to determine the selectivity of various alkyl-, aryl-, and heteroaryl-substituted hydrazines. Reactions of the aryl hydrazine 21 with the trifluoromethyl-substituted cycloalkanone 22 under neutral conditions (methanol, reflux) gave a mixture of isomers 23 and 24, whereas the reaction of the pyridyl hydrazine 25 was shown to give exclusively 26. 

The use of diphenyl hydrazone 33 has been used in the synthesis of pyrazoles under modified conditions where the hydrazine is released in situ. Some reversal of regiochemistry is seen in the reaction with unsymmetrical dicarbonyls. With aryl hydrazine and diphenyl hydrazone, the ratio of 41 to 42 is 22 1 and 5 1, respectively. 

Sanofi-Synthelabo researchers discovered pyrazole 53 and analogs to have potent Cannabinoid receptor-1 (CB-1) antagonist/inverse agonist activity and have progressed 53 into development for treatment of obesity and alcohol dependence. The synthesis of 53 was accomplished by heating the diketone sodium salt 51 with the aryl hydrazine hydrochloride in acetic acid to provide the intermediate 52, which was further derivatized... 

The hydrazones 1 used as starting materials are easily prepared by reaction of an aldehyde or ketone 8 with an aryl hydrazine 7 ... 

Disubstituted triazolium salts are prepared from alkyl or aryl hydrazines via an oxadiazolium salt 28 (Scheme 16). Addition of a chiral amine on this salt resulted in a ring opening - ring closure reaction affording the triazolium salts 29. 

Ethyl formate34,52 or orthoformate5 3,54 reacts with two equivalents of phenylhydrazine to yield 1,5-diphenylformazan (11) the reaction takes place under acidic conditions and involves an oxidation. Under basic conditions, ethyl nitrate reacts at the methylene position to yield 3-methyl-1,5-diphenylformazan (37) which can also be obtained from the reaction of phenyl-azoethane (38) with isoamyl nitrite (Scheme 4).8,68 Aryl hydrazines react with a variety of s-triazines (39) to yield 1,5-diaryl formazans with hydrogen, methyl, or phenyl groups in the 3-position as in 40 (Eq. 6).56 Hydrazines have also been reported to react with benzotrichloride55,658 and sym-diamino tetrazine659 to yield formazans. 

Palladium-catalyzed cyclization reactions with aryl halides have been used to synthesize pyrazole derivatives. V-Aryl-lV-(c>-bromobenzyl)hydrazines 26 participated in a palladium-catalyzed intramolecular amination reaction to give 2-aryl-2W-indazoles 27 . Palladium-catalyzed cascade intermolecular queuing-cyclocondensation reaction of o-iodophenol (28) with dimethylallene and aryl hydrazines provided pyrazolyl chromanones 29 <00TL7129>. A novel one-pot synthesis of 3,5-disubstituted-2-pyrazolines 32 has been achieved with an unexpected coupling-isomerization sequence of haloarene 30, propargyl alcohol 31, and methylhydrazine <00ACIE1253>. 

Carbazoles from naphthols and aryl hydrazines promoted by sodium bisulfite. 

Reaction of TeOj/LiCl with aryl hydrazines ... 

Similar to the aetivity of alkyl hydrazines that liberate alkyl radicals upon metabolic several aryl hydrazines with various para substituents (X = H, CH3,... 

CH2OH, COOH) are found in the mushroom Agaricus bisporus and are metabolized to arenediazonium ions and then to aryl radicals that form the 8-Ph-dG (X = H) adduets shown in Fig. 7. Aryl hydrazines are mutagenic in bacteria, ... 

These meso-ionic compounds are often referred to as isosydnones (146). They are prepared from )V-acyl-iV-(alkyl or aryl)-hydrazines (147, X = 0) or their hydrochlorides and carbonyl chloride. " The isosyd-... 

The benzoylmethyl-substituted condensed triazinones 118 undergo condensation with aryl hydrazines in boiling propan-2-ol or hexan-l-ol to produce the corresponding hydrazones 119 which are easily cyclized upon boiling in neat phosphorus oxychloride to give the novel condensed pyridazino[6,5-i ]-l,2,4-triazines 120 shown in Scheme 17 <1999CHE376, 1999KGS426>. 

Am Ring-N-Atom substituierte 2,5-Alkyl(Aryl)-1,3,4-oxadiazoliuni-Salze konnen in exzellenten Ausbeuten aus 1-substituierten 1,2-Diacyl-hydrazinen mit Perchlorsaure oder Tetrafluorborsaure in Acetanhydrid synthetisiert werden567 56S. Diese Methode laBt sich auch dahingehend variieren, daB man 2-Acyl-l-alkyl(aryl)-hydrazine mit Carbonsiiureanhydrid und Perchlorsaure umsetzt567,568... 

Hettche was able to add diarylaminyls, which can be generated by thermolysis of hexa-aryl-hydrazines 150 to 2.4.6-triphenyl- -phosphorin... 

Reaction of aryl hydrazines and hydrazine with dimethyl acetylene dicarboxylate to afford imine-enamine tautomers [192]. 

Powell J.H. and Gannett, P.M. (2002) Mechanisms of carcinogenicity of aryl hydrazines, aryl hydrazides, and arene diazoniumions./. Environ. Pathol. Toxicol. Oncol., 21 (1), 1-31. 

Pyrans 69 and 326 (R = Pr) provide dihydropyridines with aryl-hydrazines,311,313 but a structure proof is lacking. 

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