Synthesis of hydrazones

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A catalytic acceptorless dehydrogenative coupling of arylhydrazines and alcohols enables a direct synthesis of arylhydrazones with complete selectivity for arylhydrazones without N-alkylated byproducts. This process provides a new horizon for the development of catalytic acceptorless dehydrogenative coupling reactions.
F. Li, C. Sun, N. Wang, J. Org. Chem., 2014, 79, 8031-8039.

N-tert-butyldimethylsilylhydrazone (TBSH) derivatives from carbonyl-containing compounds serve as superior alternatives to simple hydrazones in Wolff-Kishner-type reduction reactions, in the Barton vinyl iodide preparation, in the synthesis of vinyl bromides, and in the synthesis of gem-diiodides, gem-dibromides, and gem-dichlorides.
M. E. Furrow, A. G. Myers, J. Am. Chem. Soc., 2004, 126, 5436-5445.

A variety of azides were treated with N,N-dimethylhydrazine in the presence of ferric chloride hexahydrate as catalyst in refluxing acetonitrile to provide pure hydrazones.
I. C. Barrett, J. D. Langille, M. A. Kerr, J. Org. Chem., 2000, 65, 6268-6269.

A Michael addition of amines and hydrazines to nitrostyrenes provides N-alkyl/aryl substituted benzyl imines and N-methyl/phenyl substituted benzyl hydrazones via a retro-aza-Henry-type process under mild, noncatalytic conditions. The method can be used for the synthesis of biologically important N-methyl pyrazoles in a one-pot manner, simple starting with the corresponding nitrostyrenes and the methylhydrazine.
M. G. Kallitsakis, P. D. Tancini, M. Dixit, G. Mpourmpakis, I. N. Lykakis, J. Org. Chem., 2018, 83, 1176-1184.

An electrooxidation of benzylic C(sp³)-H bonds to produce hydrazones avoids the use of hazardous metal catalysts and external oxidants in aqueous media in the presence of NaCl as cheap electrolyte. This strategy provides hydrazones with various functional groups in good efficiency while the highly oxidizable hydrazide group remains intact. The reaction is suitable for gram-scale synthesis.
I. Yavari, S. Shaabanzadeh, J. Org. Chem., 2022, 87, 15077-15085.

A facile gold-catalyzed hydrohydrazidation of alkynes with various hydrazides provides a wide range of substituted keto-N-acylhydrazones in very good yields under mild conditions. The reaction exhibits high functional group tolerance, and is insensitive to electronic and steric effects.
D. P. Zimin, D. V. Dar'in, V. A. Rassadin, V. Y. Kukushkin, Org. Lett., 2018, 20, 4880-4884.

Alkynyl hydrazones can be conveniently synthesized from 2-oxo-3-butynoates and hydrazine without formation of pyrazoles. The resultant hydrazones are transformed into alkynyl diazoacetates under mild oxidative conditions in excellent yields. Further, alkynyl cyclopropane and propargyl silane carboxylates are synthesized in good yields using copper-catalyzed alkynyl carbene transfer reactions.
A. Sharma, P. Jamwal, H. Vaid, R. Gurubrahamam, Org. Lett., 2023, 25, 1889-1894.

A mild diazenylation of active methylene compounds and N-heterocyclic compounds with arylhydrazine hydrochlorides is mediated by iodine under basic aerobic conditions. The reaction could be executed either under heating or in the presence of blue LED light.
D. S. Barak, S. U. Dighe, I. Avasthi, S. Batra, J. Org. Chem., 2018, 83, 3361-3366.