Z-phenylhydrazone

Another example of this rearrangement has been used to prepare 1,2,3-triazole 146 from furazanic phenylhydrazone 147 (Scheme 84) [93JCS(P1)2491]. Interestingly, furoxanic Z-phenylhydrazones 150 underwent thermal recyclization to 1,2,3-triazole A-oxides 152, evidently through intermediate 151. Treatment of the hydrazone 150 with rerr-BuOK leads to the nitromethyl derivative 149 [OOOMIl] (Scheme 84). Lead tetraacetate oxidation of 147 with subsequent Lewis acid treatment of the initially formed intermediate afforded indazole 148 (Scheme 84) (85JHC29). 

A 14 1 mixture of ( )- and (Z)-phenylhydrazones 249 and 250 was obtained from 2-[A-(cyclohex-2-en-l-yl)]-3-formyl-4/7-pyrido[l, 2-n]pyrimi-din-4-one 248 with PhNHNH2. Pentacyclic compound 251 was obtained from both ( )- and (Z)-phenylhydrazones 249 and 250 by heating in boiling EtOH (96T901). 

The 1H, 13C, and 15N NMR chemical shifts of the (Z)-phenylhydrazones of 5-alkyl-and 5-aryl-3-benzoyl-l,2,4-oxadiazoles have provided information on the ground-state electronic distribution.27 The effects of the substituents on the chemical shifts of N(4) and C(5) correlate with kinetic results of the rearrangement of 1,2,4-oxadiazoles to 1,2,3-triazoles (Boulton-Katritzky reaction) support the importance of the leaving group. 

Base-catalyzed isomerization (called mononuclear heterocyclic rearrangement ) was described for the formation of Z-phenylhydrazone of 3-benzoyl-l,2,4-oxadiazole 156 into 4-benzoylamino-1,2,3-triazole 157242,243 (equation 61). 

Scheme 5.1-13 Rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-l,2,4-oxadiazole in ionic liquids.

The inability of ionic liquids to interact strongly with neutral nucleophilic species has been considered recently to be the main factor determining the high rate of rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-l,2,4-oxadiazole in ionic liquids in comparison to molecular solvents (Scheme 5.1-13) [42]. 

The conversion of the (Z)-phenylhydrazone of 5-amino-3-benzoyl-l,2,4-oxadiazole into the relevant 1,2,3-triazole in the presence of several haloacetic acids and the kinetics of the rearrangement of (Z)-arylhydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole to (2-aryl-5-phenyl-2//-l,2,3-triazol-4-yl)ureas have been reported. Treatment of benzannulated enediynyl alcohols with trifluoroacetic acid promoted a cascade sequence of cyclization reactions leading to 1,4-naphthoquinone methides (Scheme 37)7 ... 

N-Benzoyl yellowish-green needles from CgHg, M.p, 193°. Spar. sol. cold EtOH. H P-Toluenesulphonyl m.p. 202-5°. Z-Phenylhydrazone m.p. 268°, 2-[4 -Methyl]-anil brownish-violet needles from CgHg. M.p. 180°, Sol. MegCO, CgH,. Mod, sol. EtOH. 

The kinetic study on the conversion of (Z)-phenylhydrazone of 5-amino-3-benzoyl-l,2,4-oxadiazole (51) into Af,5-diphenyl-2H-l,2,3-triazol-4-ylurea (52) reveals for the first time the occurrence of SA catalysis in such monocyclic rearrangement reaction.The plot of pseudo-first-order rate constants (k bs) vs. [H+] shows that the reactivity tends to a limiting rate constant. This fact suggests an SA-catalyzed mechanism according to Equation 2.43 and Equation 2.44. 

Cosimelli, B., Frenna, V., Guemelli, S., Lanza, C.Z., Macaluso, G., Petrillo, G., Spinelli, D. The first kinetic evidence for acid catalysis in a monocyclic rearrangement of heterocycles conversion of the Z-phenylhydrazone of 5-amino-3-benzoyl-... 

Analog erhalt man z. B. die 2,4-Dinitro-phenylhydrazone der folgenden Aldehyde ... 

Phenylazo-alkane lagern sich unter dem EinfluB von Radikalbildnem (z. B. Dibenzoylper-oxid), Basen (z. B. Natriummethanolat), Sauren (z. B. Schwefelsaure), Alkalien oder hohen Temperaturen in die entsprechenden Phenylhydrazone urn, wahrend die entgegengesetzte Umlagerung nicht gelingt1 ... 

Z = 0, NH), then the carbonyl group not adjacent to the heteroatom is preferentially attacked. Thus, isatin and indoxyl and their O- and 5-analogues (279, 282) react with hydroxylamine, hydrazine, phenylhydrazine, semicarbazide, etc., to give oximes, hydrazones, phenylhydrazones, semicarbazones, etc. (282 — 283 279 — 284). 

Yamamoto and Maruoka found that organoaluminum amides are highly effective in the Fischer indole synthesis. In particular, DATMP is the reagent of choice for regioselective Fischer indole synthesis [120]. For instance, treatment of the E)-N-methyl-A-phenylhydrazone of 5-methyl-3-heptanone (123) with DATMP affords 3- ec-butyl-2-ethyl-l-methylindole (125) as the sole isolable product its (Z) isomer gives l,3-dimethyl-2-(2-methylbutyl)indole (124) with high regioselectivity under similar reaction conditions, as illustrated in Sch. 84. 

Anodic oxidation of formazanes in MeCN-TEAP at a platinum anode produces tetrazolium salts in good yield [120, 121]. The ring closure probably takes place through the dication. A similar anodic coupling is the oxidation of 2-acetylpyridine phenyl-hydrazone to 3-methyl-l-phenyl-8-azaindazolium perchlorate [41], of benzilmonoxime phenylhydrazone to 2,4,5-triphenyl-1,2,3-triazole-1-oxide, and of 3-hydroxyiminomethyl-eneamino-6-chloropyridazine to 6-chloro-5-triazole[l,5-Z>]pyridazine-3-oxide [74, 122]. 

Phenyl- und 4-Nitro-phenylhydrazone konnen unter Saurekatalyse in Gegenwart von 2,4-Pentandion zu Aldehyden (und Ketonen) hydrolysiert werden34, wobei die Hydrazin-Komponente von 2,4-Pentandion durch Cyclokondensation zu l-Aryl-3,5-di-methyl-pyrazol abgefangen wird so erhalt man z.B. aus... 

Mit aromatischen Carbonsaure-chloriden sind 4-Aroyl-l H-pyrazole zuganglich, z. B. aus zwei mol Benzoylchlorid pro mol Acetophenon-phenylhydrazon 4-Benzoyl-1,3,5-triphenyl-lH-pyrazol( 100% Schmp. 174-176°) und aus 4-Methyi-acetophenon-phenylhydrazon4-Ben-zoyl-1,5-diphenyI-3-(4-methyl-phenyl)-lH-pyrazol (72% Schmp. 170- 172 )748 ... 

In z.T. guten Ausbeuten konnen Nitroformaldehyd-phenylhydrazon und analoge Ver-bindungcn durch Schwefelwasserstoff/Ammoniak zu HydroxamsSure-2-phenyI-hydraziden reduziert werden (Bd. X/4, S. 135). 

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