Large-Scale Carbonyl Reductions in the Pharmaceutical Industry

Schiff bases are a vast group of compounds characterized by the presence of a double bond linking carbon and nitrogen atoms, the versatility of which is generated in the many ways to combine a variety of alkyl or aryl substituents. Compounds of this type are both found in nature and synthesized in the laboratory. For years, Schiff bases have been greatly inspiring to many chemists and biochemists. In this article, we attempt to present a new take on this group of compounds, underlining of the importance of various types of Schiff bases. Among the different types of compounds that can be classified as Schiff bases, we chose hydrazides, dihydrazides, hydrazones and mixed derivatives such as hydrazide–hydrazones. For these compounds, we presented the elements of their structure that allow them to be classified as Schiff bases. While hydrazones are typical examples of Schiff bases, including hydrazides among them may be surprising for some. In their case, this is possible due to the amide-iminol tautomerism. The carbon–nitrogen double bond present in the iminol tautomer is a typical element found in Schiff bases. In addition to the characteristics of the structure of these selected derivatives, and sometimes their classification, we presented selected literature items which, in our opinion, represent their importance in various fields well.

https://www.mdpi.com/1420-3049/27/3/787/pdf

Different Schiff Bases—Structure, Importance and Classification

Natural hydrazine-containing compounds: Biosynthesis, isolation, biological activities and synthesis.

(7-Hydroxy-2-oxo-2 H -chromen-4-yl)-acetic acid hydrazide ( 2 ) was prepared from (7-hydroxy-2-oxo-2 H -chromen-4-yl)-acetic acid ethyl ester ( 1 ) and 100% hydrazine hydrate. Compound 2 , is the key intermediate for the synthesis of several series of new compounds such as Schiff’s bases 3a-l , formic acid N'-[2-(7-hydroxy-2-oxo-2 H -chromen-4-yl)acetyl] hydrazide ( 4 ), acetic acid N'-[2-(7-hydroxy-2-oxo-2 H -chromen-4-yl)-acetyl] hydrazide ( 5 ), (7-hydroxy-2-oxo-2 H -chromen-4-yl)-acetic acid N'-[2-(4-hydroxy-2-oxo-2 H -chromen-3-yl)-2-oxoethyl] hydrazide ( 6 ), 4-phenyl-1-(7-hydroxy-2-oxo-2 H -chromen- 4-acetyl) thiosemicarbazide ( 7 ), ethyl 3-{2-[2-(7-hydroxy-2-oxo-2 H -chromen-4-yl)-acetyl]hydrazono}butanoate ( 8 ), (7-hydroxy-2-oxo-2 H -chromen-4-yl)-acetic acid N'-[(4-trifluoromethylphenylimino)methyl] hydrazide ( 9 ) and (7-hydroxy-2-oxo-2 H -chromen-4-yl)acetic acid N'-[(2,3,4-trifluorophenylimino)-methyl] hydrazide ( 10 ). Cyclo- condensation of compound

https://www.mdpi.com/1420-3049/11/2/134/pdf

Synthesis and antimicrobial activity of some derivatives of (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid hydrazide.

Synthesis of novel derivatives of oxindole, their urease inhibition and molecular docking studies.

The standard method for preparing carboxylic acid hydrazides is hydrazinolysis of esters in alcoholic solutions. However, when applied to α,β-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 α,β-unsaturated acids. This process gives the desired hydrazides in excellent yield and purity under mild conditions.

A New Procedure for Preparation of Carboxylic Acid Hydrazides

The present invention is directed to a novel process for the preparation of tetrahydroquinolinyl derivatives useful as in the treatment of disorders and conditions modulated by the cholesteryl ester transfer protein (CETP).

Process for the preparation of tetrahydroquinolinyl, benzoxazine and benzothiazine derivatives

The present invention is directed to N-[2-[[(diaminomethylene)amino]oxy]ethyl]-3-[(2,2-difluoro-2-phenylethyl)amino]-6-methyl-2-oxo-1(2H)-pyrazineacetamide, pharmaceutical compositions containing said compound and methods of treatment comprising inhibiting a serine protease using said compound. The present invention is further directed to a process for the preparation of the N-[2-[[(diaminomethylene)amino]oxy]ethyl]-3-[(2,2-difluoro-2-phenylethyl)amino]-6-methyl-2-oxo-1(2H)-pyrazineacetamide as a free base. The present invention is further directed to a process for the preparation of pharmaceutically acceptable salts of N-[2-[[(aminoiminomethyl)amino]oxy]ethyl]-3-[(2,2-difluoro-2-phenylethyl)amino]-6-methyl-2-oxo-1(2H)-pyrazineacetamide.

N-[2-[[(diaminomethylene)amino]oxy]ethyl]-3-[(2,2-difluoro-2-phenylethyl)amino]-6-methyl-2-oxo-1(2h)-pyrazineacetamide

Reaction safety: A critical parameter in the development of a scaleable synthesis of 2,3-bis-chloromethylpyridine hydrochloride

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A New Procedure for Preparation of Carboxylic Acid Hydrazides

Process for the preparation of tetrahydroquinolinyl, benzoxazine and benzothiazine derivatives

N-[2-[[(diaminomethylene)amino]oxy]ethyl]-3-[(2,2-difluoro-2-phenylethyl)amino]-6-methyl-2-oxo-1(2h)-pyrazineacetamide

Reaction safety: A critical parameter in the development of a scaleable synthesis of 2,3-bis-chloromethylpyridine hydrochloride