Effect of the nucleophile structure and basicity on pyridine-catalyzed formation of thiosemicarbazides

The kinetics of pyridine-catalyzed reaction of O,O-diaryl hydrazidothiophosphates with phenyl isothiocyanate in benzene at 25°C were studies. Pyridine was found to exhibit a considerable catalytic effect in the formation of phosphorus-containing thiosemicarbazides. A correlation between the reactivity of phosphorus hydrazides in the catalytic reaction and their structure was revealed. The catalytic activity of pyridine increases as the basicity of hydrazide decreases. The effects of the substituents in the aromatic rings and the basicity of hydrazides weaken in going from the noncatalytic to catalytic process. The catalysis by pyridine conforms to the general base catalysis pattern.     

The hydrazide/hydrazone click reaction as a biomolecule labeling strategy for M(CO)3 (M = Re, (99m)Tc) radiopharmaceuticals

Facile reactivity of hydrazides and aldehydes was explored as potential coupling partners for incorporation into M(CO)(3) (M = Re, (99m)Tc) based radiopharmaceuticals. Both 'click, then chelate' and 'prelabel, then click' synthetic routes produced identical products in high yields and lacked metal-hydrazide/-hydrazone interactions, highlighting the potential of this click strategy.     

A Cascade Synthesis of Aminohydantoins Using In Situ‐Generated N‐Substituted Isocyanates

Nitrogen‐substituted isocyanates are rarely utilized but powerful building blocks for the development of cascade reactions in heterocyclic synthesis. These reactive amphoteric intermediates can be accessed in situ via an equilibrium that allows controlled reactivity in the presence of bifunctional partners such as α‐amino esters. A cascade reaction has been carried out that forms 3‐aminohydantoin derivatives using simple phenoxycarbonyl derivatives of hydrazides and hydrazones as precursors of N‐substituted‐isocyanates. This method allows rapid assembly of complex aminohydantoin derivatives, including analogues of medicinally‐relevant compounds, using simple reactants.     

A new procedure for preparation of carboxylic acid hydrazides

The standard method for preparing carboxylic acid hydrazides is hydrazinolysis of esters in alcoholic solutions. However, when applied to alpha,beta-unsaturated esters, the main product typically is the pyrazolidinone resulting from an undesired Michael-type cyclization. Other alternative methodologies reported for direct preparation of hydrazides from acids are inefficient. We developed an efficient and general process, involving preforming activated esters and/or amides followed by reaction with hydrazine, for the preparation of hydrazides including those of alpha,beta-unsaturated acids. This process gives the desired hydrazides in excellent yield and purity under mild conditions.     

Copper‐Catalyzed Aerobic Oxidative Reaction of Sulfonyl Hydrazides with Alcohols: An Easy Access to Sulfinates

A Cu‐catalyzed aerobic oxidative reaction between sulfonyl hydrazides and alcohols has been developed. In this reaction, sulfonyl hydrazides act as the sulfinic acid precursors to react with alcohols, resulting in sulfinic esters with up to 72 % yield. This catalytic system tolerates a wide range of sulfonyl hydrazide substrates, and represents a new strategy for the transformation of readily available sulfonyl hydrazides.     

A new synthesis of pyrazolo[1,5-d][1,2,4]triazines from pyrazolecarboxylic acid hydrazides and carbonyl compounds. I

Pyrazolo[1,5-d][1,2,4]triazines were synthesized from pyrazolecarboxylic acid hydrazides and carbonyl compounds. Pyrazolecarboxylic acid N-phenylhydrazide (1c) and formaldehyde gave not only the expected 4hn but 5 , respectively. The methyl substituted hydrazides with acetone afforded hydrazones, pyrazolotriazines or 13 depending on the position of the substituents. The reduction of both products yielded pyrazolecarboxylic acid hydrazides.     

Palladium-catalyzed desulfitative arylation of azoles with arylsulfonyl hydrazides

Palladium-catalyzed desulfitative and denitrogenative arylation of azoles with arylsulfonyl hydrazides has been achieved. A broad scope of azoles and arylsulfonyl hydrazides has been used to produce arylated azoles in high yields.     

Cyclic 1,2-dinitrogen compounds through N,N′-di(methoxycarbonyl)hydrazinium intermediates

Acid catalyzed cyclization of methoxymethyl substituted acyclic hydrazides 4 provides cyclic hydrazides 5 in moderate to good yields through the intermediacy of N,N′-di(methoxycarbonyl)hydrazinium intermediates.     

Metal-free sulfonylation of quinones with sulfonyl hydrazides in water: Facile access to mono-sulfonylated hydroquinones

This paper describes a simple and practical protocol for the direct synthesis of monosulfonylated hydroquinones through a transition-metal-free cross-coupling between quinones and sulfonyl hydrazides in water. The procedure tolerates a variety of quinones and widely available sulfonyl hydrazides.     

Synthesis pathway to carbohydrate-derived salicylidene hydrazides as ligands for oxovanadium complexes

Salicylidene hydrazides represent important ligands forming oxovanadium complexes. Carbohydrate-derived chiral salicylidene hydrazides as ligands for metal ion complexation were synthesized for the first time. The pathway of the mild and selective synthesis starts from commercial saccharides like methyl-α-d-glucopyranoside and methyl-α-d-mannopyranoside. All synthesized carbohydrate-derived salicylidene hydrazides are able to form oxovanadium complexes. The mononuclear structure proposed for the complex of 1,2,3,4-tetra-O-methyl-α-d-glucopyranuronic acid salicylidene hydrazide is consistent with the analytical data (NMR, IR and MS).     

Preparation of Hydrazides Using Silicon Tetrachloride as Coupling Agent1

Silicon tetrachloride proved to be an effective reagent for the preparation of hydrazides from carboxylic acids. Yields were comparable to those obtained via N,N′-dicyclohexylcarbodiimide (DCC) and the procedure was used to synthesize some hydrazides which are difficult to obtain otherwise.     

An Efficient Synthesis of Sulfonylhydrazides and Sulfonylsemicarbazides by Utilizing Alumina as a Catalyst

Sulfonyl hydrazides and sulfonyl semicarbazides are readily prepared by the reacting of hydrazine derivatives with sulfonyl chlorides in the presence of basic alumina under solvent‐free conditions. Reaction of a sulfonyl chloride with t‐butylcarbazate, followed by hydrolysis provides the corresponding sulfonyl hydrazides in higher yield and shorter time than previously reported.     

Acid-catalyzed rearrangement of diaryl hydrazides for the efficient synthesis of functionalized 2,2'-diamino-1,1'-biaryls

Diaryl hydrazides prepared from the Pd(0)- or Cu(I)-catalyzed coupling reactions of aryl hydrazides and aryl halides underwent the acid-catalyzed rearrangements to a series of previously unknown 2,2'-diaminobiaryls in good overall yields. The mildness of the reaction conditions allows the presence of various functional groups.     

Palladium-catalyzed direct arylation of N-heteroarenes with arylsulfonyl hydrazides

Hydrazides applied: A palladium-catalyzed direct C?H arylation of heteroarenes, with arylsulfonyl hydrazides as the arylating reagents, has been developed. The reaction is chemoselective, in that arylsulfonyl hydrazides containing halogen substituents can be employed without participation of the halogen substituent in the reaction. The method offers a straightforward approach to a variety of aryl-heteroaryl compounds.     

Solvation and Complex Formation of Nickel(II) with Benzoic,p-Chlorobenzoic,and p-Methoxybenzoic Hydrazides in Aqueous-Dioxane Media

Solvation and complex formation of nickel(II) with benzoic, p-chlorobenzoic, and p-methoxybenzoic hydrazides in aqueous-dioxane media were studied. The mean coordination numbers of water and 1,4-dioxane in Ni(II) solvation complexes, the formation constants of mono- and biscomplexes of nickel(II) of the listed hydrazides at dioxane contents of 0-0.65 mole fraction, as well as the free energies of transfer of the ligands from water to aqueous-dioxane solvents were determined. An important role the basicity and solvation of the ligands play in te stability of Ni(II) complexes with benzoic hydrazides was demonstrated.     

Preparation of hydrazides of amino acids and peptides

A new method of synthesizing hydrazides of amino acids and peptides is considered which involves the hydrazinolysis of the silyl esters of the corresponding compounds. A number of hydrazides of derivatives of amino acids and peptides has been obtained in high purity with yields close to quantitative. The physicochemical characteristics of the compounds synthesized are given.     

Synthesis of Derivatives of 1-(9-Alkyl-9H-carbazol-3-yl)-4-carboxy-2-pyrrolidinones

Derivatives of 1-(9-alkyl-9H-carbazol-3-yl)-4-carboxy-2-pyrrolidinones (methyl esters, hydrazides) were synthesized. The condensation of the synthesized hydrazides with aromatic aldehydes, acetylacetone, and acetoacetic ester was studied. Structure of the obtained compounds was confirmed by IR and NMR spectroscopy. The specific characteristics of the substituents are discussed.     

Synthesis of hydrazones derived from 2-substituted-10-carboxyphenothiazine hydrazides

2-Substituted-10-carboxyphenothiazine hydrazides 3 were found to yield hydrazones 5 on reaction with aromatic aldehydes. However, a similar reaction of hydrazides 3 with aliphatic ketones in refluxing ethanol failed to give the expected hydrazones 6 . The corresponding phenothiazines 1 were isolated in this reaction, apparently through alcoholysis of the amide bond to the ring nitrogen atom in 3 .     

Pyrrolo[1,2-d]triazines-1,2,4. I. Dérivés pyrroliques

Pyrrole hydrazides and hydrazones were synthesized from pyrrole-2-carboxylic acid and pyrrole-2-carboxaldehyde, The 2-pyrrolyloxadiazoles and thiadiazoles were obtained by cyclising the pyrrole hydrazides with phosphorus oxychloride and tetraphosphorus decasulphide. These derivatives have been used for the synthesis of pyrrolo[1,2-d]-1,2,4-triazines by cyclisation or rearrangement.     

Synthesis of N′-cyclohexenecarbonyl-substituted hydrazides of 2-aminobenzoic acids and preparation of 3-cyclohexenyl-amido-1,2-dihydroquinazolin-4-ones based on them

N′-Cyclohexenecarbonyl-substituted hydrazides of 2-aminobenzoic acids were obtained from the reaction of isatoic anhydride with monohydrazides of cyclohexenedicarboxylic acid. Reaction of the 2-aminobenzoic acid hydrazides with substituted benzaldehydes gave 3-cyclohexenylamido-1,2-dihydroquinazolin-4-ones. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, 894–898, June, 2007.