Carboxylic acid hydrazides

Thiazole carboxylic acid hydrazides were prepared in a similar way (444, 445). Thus by refluxing thioacetamide or thiobenzamide with y-bromoaceto acetic ester arylhydrazones (83) for several hours in alcohol the 4-carboxythiazole derivatives (84) listed in Table II-ll were obtained (Scheme 36) (656). This reaction is presumed to proceed via dehydration of the intermediate, thiazoline-S-oxide. 

TABLE XXIX. l-Methyl-l,6-dihydropyrazolo[3,4-(i]pyridazm-7-ones Prepared by Cyclization of 4-(Alkyn-1 -yl)pyrazole-5-carboxylic Acid Hydrazides [85IZV1367 85MI2]. 

Only one report is concerned with the synthesis, molecular structure, and X-ray analysis of this ring system as 2 (86KGS477). The synthesis of 2 was achieved by the cyclization of 2-aziridine carboxylic acid hydrazide with acetone as shown in Scheme 2. 

Reaction of benzimidazole-2-carboxylic acid hydrazide 590 with carbon disulfide gave triazine 591 (86JPR515) (Scheme 121). 

Pyrazolones have been prepared by palladium promoted cyclization of a,/ -unsaturated carboxylic acid hydrazides but yields are only moderate (Scheme 91)15 6 and no attempt has been made to effect a catalytic conversion. 

Aminopyrazole has been prepared by a Curtius degradation of pyrazole-3(5)-carboxylic acid hydrazide,2 3 by saponification and decarboxylation of ethyl 3-aminopyrazole-4-carboxy-late 4 obtained from ethyl ethoxymethylenecyanoacetate and hydrazine, and by the present procedure.6,6... 

Carboxylic acid hydrazides, 13 574 Carboxylic acid layer, on polymer surfaces, 20 379-380... 

Isocarboxazid Isocarboxazid, 2-benzylhydrazid-5-methyl-3-isoxazolecarboxylate (7.2.6), can be synthesized from acetylacetone, which on nitrosation with nitrous acid gives 5-methyl-isoxazol-3-carboxyhc acid (7.2.2). Esterification of this product gives the ethyl ester of 5-methyl-isoxazol-3-carboxyhc acid (7.2.3). The synthesized ester (7.2.3) is further reacted with benzylhydrazine, to give isocarboxazide (7.2.6), or with hydrazine, which forms 5-methyl-isoxazol-3-carboxylic acid hydrazide (7.2.4). Reacting the latter with benzaldehyde gives hydrazone (7.2.5), which is further reduced to the isocarboxazide (7.2.6) [46,47]. 

The first inhibitors of flavin-dependent MAO that were developed for clinical use were hydrazines and hydrazides. The chance discovery that the antitubercular drug, 4-pyridine carboxylic acid hydrazide (isoniazid, 40), was also a potent MAO inhibitor led to the development of the related drug, iproniazid (41), used for the treatment of depressive illness. Although this compound demonstrated remarkable antidepressant action, its clinical value was seriously compromised by side effects [19]. 

Table 37 Actinide(IV) Complexes with Carboxylic Acid Hydrazides, RCONHN=CHR1...

Table 78 Some Complexes of Carboxylic Acid Hydrazides with Dioxouranium(VI) Compounds...

Amino-S-hy droxy-1,2,3-triazole-4-carboxylic acid hydrazide 1 A218... 

Ami no-5-hydroxy-1,2,3-triazole- 4 carboxylic acid hydrazide or 1-Amino-4-hydrazido-carbon-5-hydroxytri azole,(Called 1-Amino-4-hydrazidocarbon-5 oxytriazoI in Ref 2), HO-C-N(NH ) N, mw 158.13, N... 

Bisoxadiazoles are formed from bis(mono)imido ester hydrochlorides and mono(bis)carboxylic acid hydrazides when the free ester is used, an amidrazone (27) is often formed which cyclizes with the elimination of ammonia to give 28.73 The reaction proceeds in the presence of higher boiling solvents or by mixing the reactants at a temperature higher than 100°, the imido esters forming first in the reaction mixture. The reaction of semicarbazide [Eq. (2), R = NH2] with imido esters does not, of course, lead to 2-amino-1,3,4-oxadiazoles but to the isomeric l,2,4-triazolin-3-ones.72 The reaction of N-substituted imidochlorides with aromatic acid hydrazides in the... 

Benzyloxyindole-2-carboxylic acid hydrazide and arylidene hydrazides undergo fragmentation with significant loss of hydrazine and arylidenehydrazine radicals as well as of neutral isocyanates <2005JHC985>. 

Compounds such as 543 and 545 were prepared either from 5-hydrazino-1,4-benzodiazepines (e.g. 542), by cyclization (78JHC1127) with carboxylic acid derivatives, or from 1,4-benzodiazepine-5-imidates (e.g. 544, Z = OMe) (7ITL1609), 5-thioimidates (e.g. 544, Z = SMe) (78JHC1127), or 5-imidoyl chlorides (e.g. 544 Z = Cl) (76TL1931 77TL1699) with carboxylic acid hydrazides. 

The reduction of acyl hydrazines has been investigated very little. Polarography of 4-pyridine carboxylic acid hydrazide in acid and neutral solution shows that it is reduced in two, two-electrons steps [141]. The result of controlled potential electrolysis is cleavage of the N-N bond to form 4-pyridine-carboxamide, which then undergoes reduction to the aldehyde in the second step. Other hydrazides of heterocyclic carboxylic acids behave analogously. 

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