Carboxylic acid hydrazides 1-acyl

Examples of the synthesis of other hydrazides from carboxylic acids and acyl- or alkylhydrazines are provided below [75] [171]... 

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. 

The products of the reaction between carboxylic acid hydrazides and carbon disulfide cyclize very readily to Zl4-l,3,4-oxadiazoline-2-thiones (LXXXIII) (see Section II.7). The intermediates, the acyl- or benzoyl-dithiocarbazic acids may, however, also be isolated and reacted with alkyl halides to give S-alkyl dithiocarbazates (LXXXVIIIa) which also cyclize easily either to thiadiazoline or oxadiazoline rings according to the reaction circumstances (see Section II.7). 

Potassium hydrogen carbonate l-Acyl-4-ureidosemicarbazides from carboxylic acid hydrazides... 

Acyl halogenosulfonates 32, 459 Acylhydrazines (s. a. Carboxylic acid hydrazides, Sulfonic —) -, N-benzylation 31,264... 

Much of the evidence for this route came from the initially surprising oberservation that acridine 9-carboxylic acid hydrazide gave not the excited carboxylate, but emission from acridone. Strong support for the acyl anion route is obtained from the fact that 9-formyl acridine in strong base is highly chemiluminescent [80]. 

Carboxylic acid hydiazides are prepared from aqueous hydrazine and tfie carboxylic acid, ester, amide, anhydride, or halide. The reaction usually goes poody with the free acid. Esters are generally satisfactory. Acyl halides are particularly reactive, even at room temperature, and form the diacyl derivatives (22), which easily undergo thermal dehydration to 1,3,4-oxadiazoles (23). Diesters give dihydtazides (24) and polyesters such as polyacrylates yield a polyhydrazide (25). The chemistry of carboxyhc hydrazides has been reviewed (83,84). 

Claisen ester condensation, 6, 279 Thiazolecarboxylic acid chlorides reactions, 6, 279-280 Thiazolecarboxylic acid hydrazides synthesis, 6, 280 Thiazolecarboxylic acids acidity, 6, 279 decarboxylation, 6, 279 reactions, S, 92 6, 274 Thiazole-2-carboxylic acids decarboxylation, S, 92 Thiazole-4-carboxylic acids stability, S, 92 Thiazole-5-carboxylic acids decarboxylation, S, 92 Thiazole-4,5-dicarboxylic acid, 2-amino-diethyl ester reduction, 6, 279 Thiazole-4,5-dicarboxylic acids diethyl ester saponification, 6, 279 Thiazolediones diazo coupling, 5, 59 Thiazoles, 6, 235-331 ab initio calculations, 6, 236 acidity, S, 49 acylation, 6, 256 alkylation, S, 58, 73 6, 253, 256 analytical uses, 6, 328 antifogging agents... 

The acyl azide intermediates are prepared either by reaction of sodium azide with a reactive acylating agent or by diazotization of an acyl hydrazide. An especially convenient version of the former process is treatment of the carboxylic acid with ethyl chloroformate to form a mixed anhydride, which then reacts with azide ion.265... 

Much more important than these reactions, however, are the reactions of CDI and its analogues with carboxylic acids, leading to AAacylazoles, from which (by acyl transfer) esters, amides, peptides, hydrazides, hydroxamic acids, as well as anhydrides and various C-acylation products may be obtained. The potential of these and other reactions will be shown in the following chapters. In most of these reactions it is not necessary to isolate the intermediate AAacylazoles. Instead, in the normal procedure the appropriate nucleophile reactant (an alcohol in the ester synthesis, or an amino acid in the peptide synthesis) is added to a solution of an AAacylimidazole, formed by reaction of a carboxylic acid with CDI. Thus, CDI and its analogues offer an especially convenient vehicle for activation of... 

As in Section 5.06.9.1, the assignments are sometimes arbitrary. Important routes to oxadiazoles, aminooxadiazoles, oxadiazolinones, and oxadiazolinethiones involving the reaction of hydrazides RCONHNH2 with carboxylic acids, acyl chlorides, alkyl esters, or trialkyl orthoesters are described in Section 5.06.9.2.1, reactions with carbon disulfide... 

Monothiodiacylhydrazines 127, derived from the acylation of thiosemicarbazides or as intermediates in the reactions of (1) thiohydrazides with carboxylic acids and their derivatives (see Section 5.10.9.2.2(i)) or (2) hydrazides with thiocarbonyl compounds (see Section 5.10.9.2.3(i)), cyclize in the presence of an acid catalyst to give 1,3,4-thiadiazoles 128 (Equation 39, Table 4). 

Benzotriazoles are neutral acylating agents, successfully used for the preparation of amides, oxamides and hydrazides The acylbenzotriazoles 95a-d are prepared from carboxylic acids 94a-d by reaction with l-methanesulfonyl-l//-benzotriazole (Scheme 51). Reaction of 1-benzoyl-l//-benzotriazole with hydroxylamine hydrochloride in the... 

Reactions of pyrimido[4,5-3] [l,4]thiazines were discussed in CHEC-II(1996) <1996CHEC-II(7)737> more recently, reported reactions of this system involve nucleophilic substitution in a number of guises. Hemiaminals at C-3 react with ammonium acetate to form aminals (Equation 166) <1999CHE97>. The formation of acyl hydrazides from pyrimido[4,5-3][l,4]thiazine-2-carboxylic acids, along with their subsequent conversion to acyl azides and Curtius... 

Treatment of salicylic hydrazide in toluene with a single carbon insertion unit, such as carboxylic acid anhydride, acid chloride, and orthoester, in the presence of an equimolecular amount of methanesulfonic acid gave the l,3,4-benzoxadiazepin-5-ones (530) (43-68% yield), via the O-acylation intermediates (529) (92S929). 

This chapter includes not only nuclear and extranuclear pyrazinecarboxylic acids and anhydrides, but also the related esters, acyl halides, amides, hydrazides, nitriles, aldehydes, ketones, and any of their thio analogues a few rare isothiocyanatopy-razines and pyrazinecarbonitrile oxides are also included. To avoid repetition, interconversions of these pyrazine derivatives are discussed only at the first opportunity for example, the esterification of carboxylic acids is discussed as a reaction of carboxylic acids rather than as a preparative route to carboxylic esters, simply because the section on carboxylic acids precedes that on carboxylic esters. To minimize any confusion, many cross-references have been inserted. 

Carboxy includes carboxy (carboxylic acids), alkoxycarbonyl (esters), carbamoyl (amides), thiocarbamoyl, hydrazinocarbamoyl (hydrazides), guanidinocarbonyl, azidocarbonyl (azides), chlorocarbonyl (acid chlorides), amidino, C-hydrazino-C-iminomethyl, C-alkoxy-C-iminomethyl (imino ethers), C-alkylthio-C-iminomethyl (iminothioethers), cyano (nitriles), C-formyl(aldehydes), dialkoxymethyl (acetals of aldehydes), C-acyl (ketones), isocyanato, and thiocyanato groups. 

This chapter is concerned with the cathodic reduction of carboxylic acids and their derivatives, that is, esters, amides, anhydrides, acyl halides, hydrazides, nitriles, and corresponding thio derivatives. Cyclic derivatives of substituted carboxylic and polycarboxylic acids, such as lactones, lactams, imides, and anhydrides, are also included. Only those transformations in which the functional group itself is involved are discussed. Reductive coupling of carboxylic acids and derivatives is covered in Chapter 22, and there is some overlap with reduction of heterocycles in Chapter 18. 

---