Hydrazides, rearrangement

An alternative to the synthesis of arylsulfonylmethylcarbamates by the Mannich condensation as described here, is the Curtius rearrangement of the hydrazides of arylsulfonylacetic acids. 

The conversion of a 4-arylazo-5-oxazolone into a 1,2,4-triazole by reaction with a Grignard reagent is mentioned in Section II, B, 3. In HiTnilar fashion, the rearrangement of compound 30 to derivatives of 3-carboxy-l,5-diphenyl-lfl -l,2,4-triazoles (40) proceeds readily in the presence of strong nucleophiles [Eq. (26)]. This transformation undoubtedly occurs by ring opening and dehydrative cychzation, and, indeed, the acyclic amide and hydrazide 41 have been isolated. ... 

The methyl ester 2 can be converted into the trithiatriazepinamine 12 via the hydrazide 9. Nitrosation gives the azide 10. which undergoes a Curtius rearrangement to the isocyanate 11, which is not isolated but hydrolyzed in situ to the amine 12.418... 

The lH-l,2,4-triazole compounds possess important pharmacological activities such as antifimgal and antiviral activities [18-20]. In the present study, the reactive intermediates 45a-c, prepared in situ from the dichlorides 44a-c, were reacted via the cycloaddition reaction with ethyl cyanoacetate 40 to give, after spontaneous rearrangement, the triazole hydrazides 41a-c. These compoimds were used as starting materials for the synthesis of the... 

R =R =ArO R =Me or 4-nitrophenyl) in the presence of tert-butylamine do not rearrange but instead afford the amides (236) and the hydrazides (237). Some liberation of phenol may occur from (227 R1=ArO R =Ar) and thiswould arise either by attack by MeO- at phosphorus, or by elimination from the... 

Scheme 166 shows application of this methodology for preparation of hydrazide 1007. Thus, the reaction of acid 1004 with 1-hydroxybenzotriazole and EDC [l-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride] gives ester 1005 that can be separated and characterized, but it rearranges slowly to isomeric form 1006 in solutions. However, both derivatives, 1005 and 1006, are found to be equally reactive toward hydrazine and afford hydrazide 1007 in 98% isolated yield <2002JOC9471>. 

Treatment of a solution of 2-benzothiazolylthioacetyl hydrazide 386 in ethanol with carbon disulfide in the presence of potassium hydroxide gives the rearrangement product [l,2,4]triazolo[3,4- ]benzothiazole-3-thiol 387 (unreported yield) (Scheme 43). The structure of this compound was confirmed by its analytical and spectroscopic data, and confirmed by unequivocal synthesis from 2-benzothiazolhydrazine 388 under the same experimental conditions <2002MI3, 2002MI4>. 

By analogy with the conversion of 1,2-dialkylpyridinium salts into 2-alkylaminopyridines known as the Kost-Sagitullin rearrangement, the pyridinium salt 252 was treated with two different hydrazides (Equation 33). The [l,2,4]triazolo[4,3-tf]-pyridines 253 with Y = 4-pyridyl and NH2 were obtained with 35% and 38% yields, respectively <2003CHE275>. 

Isomorphic monomers, 19 762 Isoniazid, 25 798 Isonicotinic hydrazide, 21 103 Isonitrile complexes, platinum, 19 656 Isonitrile-nitrile rearrangement, 21 149 Isononanoic acid, physical properties, 5 35t Isononyl alcohol, properties of commercial, 2 12t... 

Spirocyclic oxindole 60 was synthesized by [3,3]-sigmatropic rearrangement of the Af-phenyl-O-acylhydroxamic acid 58 (equation 19). The potassium enolate formed by treatment of 58 with potassium hexamethyldisilazide at low temperature rearranged to 59, which easily cyclized to the spirocyclic oxindole 60. Spirooxindoles were previously synthesized by Wolff and Taddei. The spirooxindole 60 was formed in 51% yield from cyclohexanecarboxylic acid after heating the preformed lithium salts of phenyl hydrazide 61 to 205-210 °C. 

Af, A -Disubstituted hydrazones rearrange smoothly to furnish 1,2,3-triazolium salts, hydrazides give triazolones (35), and amidrazones (36) afford (37) (Scheme 12) <91KGS822,92KGS969). 

Curtius rearrangement of a-oximino acid azides is reported as a new method of synthesis for 3-substituted 5-hydroxyoxadiazoles. In this method, the oxime of an a-ketoester is converted to the acid hydrazide, which in turn is converted to the azide by reaction with nitrous acid 115a). 

In a rearrangement reaction, 2-hydroxy-2-phenyl-2-(3-pyridinyl)acetic hydrazide, 102, reacts with methanesulfonyl chloride to generate a mixture of pyrrolo[2,3-. ]pyridine derivatives (Equation 42) <1998JHG145>. The proposed mechanism for the rearrangement involves intramolecular attack of compound 102 on a reactive pyridinium intermediate formed during the reaction. 

Betaines 261 are stable crystalline compounds. Knowledge of their chemical reactions is still limited. Alkaline hydrolysis of aryl derivatives (261 R = Ar) gives the 2-azobenzoic acids 266 but the mechanism of this rearrangement is unknown. Reduction by tin and hydrochloric acid gives the hydrazides 267. Thermolysis of the p-tolyl compound (261 R = p-MeC6H4) (120 C at 0.1 mm Hg) gives the isomeric triazine (268 R = >-MeC6H4). Phosphorus pentasulfide converts the 2-methyl derivative (261 R = Me) into 2-methyl l,2,3-benzotriazinium-4-thiolate (272 R = Me) (Section in,B,15). 

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