A tosylhydrazone in organic chemistry is a functional group with the general structure RR'C=N-NH-Ts where Ts is a tosyl group. Organic compounds having this functional group can be accessed by reaction of an aldehyde or ketone with tosylhydrazine.
As an example camphor tosylhydrazone is synthesised by condensation of camphor and tosylhydrazine in ethanol with hydrochloric acid catalysis.
Reactions Hydrolysis is the reverse reaction of formation with regeneration of the carbonyl compound.
In the Shapiro reaction tosylhydrazones are used as a leaving group in elimination reactions. This reaction requires a strong base. If sodium methoxide is used as the base the reaction is called a Bamford–Stevens reaction. Tosylhydrazones can be reduced to the corresponding alkanes with reagents such as sodium borohydride and borane.
Tosylhydrazone salts can react with metals to form metal carbenes and used in cyclopropanations and epoxidations. A New Protocol for the In Situ Generation of Aromatic, Heteroaromatic, and Unsaturated Diazo Compounds and Its Application in Catalytic and Asymmetric Epoxidation of Carbonyl Compounds. Extensive Studies To Map Out Scope and Limitations, and Rationalization of Diastereo- and Enantioselectivities Varinder K. Aggarwal, Emma Alonso, Imhyuck Bae, George Hynd, Kevin M. Lydon, Matthew J. Palmer, Mamta Patel,, Marina Porcelloni, Jeffery Richardson, Rachel A. Stenson, John R. Studley, Jean-Luc Vasse, and Caroline L. Winn Journal of the American Chemical Society 2003 125 (36), 10926-10940 Fulton, J. R., Aggarwal, V. K. and de Vicente, J. (2005), The Use of Tosylhydrazone Salts as a Safe Alternative for Handling Diazo Compounds and Their Applications in Organic Synthesis. European Journal of Organic Chemistry, 2005: 1479–1492. An example of a transition metal-catalyzed cyclopropanation is a synthesis of tranylcypromine,Catalytic Cyclopropanation of Alkenes Using Diazo Compounds Generated in Situ. A Novel Route to 2-Arylcyclopropylamines Varinder K. Aggarwal, Javier de Vicente, and Roger V. Bonnert Org. Lett.; 2001; 3(17) pp 2785 - 2788; in which the sodium salt of benzaldehyde tosylhydrazone is converted to a rhodium metal carbene through the diazo intermediate.
Tosylhydrazones are also starting materials for certain cross-coupling reactions.Barluenga, J. and Valdés, C. (2011), Tosylhydrazones: New Uses for Classic Reagents in Palladium-Catalyzed Cross-Coupling and Metal-Free Reactions. Angewandte Chemie International Edition, 50: 7486–7500. As part of the catalytic cycle the diazo intermediate formed by decomposition of the tosylhydrazone gives a palladium-carbene complex with the oxidative addition complex of palladium with the aryl halide.
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