Recent Advances in Transition-Metal-Catalyzed Reactions of N-Tosylhydrazones

Abstract

N-Tosylhydrazones are highly versatile precursors for in situ carbene formation and are frequently used in metal-catalyzed cross-coupling reactions. Due to their many applications in organic synthesis, including C–C, C–O, C–N, and C–S bond formation, N-tosylhydrazones have recently received much interest. They can be simply synthesized by reacting an aldehyde or ketone with N-tosylhydrazine to produce a solid N-tosylhydrazone, which is a ‘green’ precursor of diazo compounds. Using a suitable metal catalyst, N-tosylhydrazones show versatile substrate scope for the synthesis of substituted diaminopyrroles, chromenopyrazoles, alkenylpyrazoles, benzofuran thioethers, tetrahydropyridazines, sulfur-containing heterocycles, and benzofurans with potent biological activities and even regioselective N-functionalization reactions. Metal-catalyzed reactions of N-tosylhydrazones for the construction of bioactive heterocycles are still highly in demand. Hence, this review focuses on the recent synthetic application of N-tosylhydrazones influenced by different transition metals with notable features like simple workup procedures, gram-scale synthesis, broad substrate scope, multicomponent processes, cyclization, and carbon–heteroatom bond formation.1 Introduction2 Applications of N-Tosylhydrazones3 Conclusion

I2/DMSO-mediated oxidative C–C and C–heteroatom bond formation: a sustainable approach to chemical synthesis

“…Additionally, the utilization of affordable and easily accessible reactants enhances the practicality of this methodology. 98,99 The functional group tolerance on aromatic enaminones is very good, whereas alkyl enaminones are incompatible to achieve the targeted product (Scheme 57).…”

Who is Who in the Carbene Chemistry of N‐Sulfonyl Hydrazones

“…[ 8‐9 ] Among various carbene precursors, N ‐sulfonyl hydrazones have gained substantial attention thanks to their ready availability from carbonyl compounds, stability, and sustainability. [ 10‐19 ] Historically, the first application of N ‐sulfonyl hydrazones appeared in 1952 when Bamford and Stevens reported the decomposition of N ‐tosylhydrazones by a strong alkali to give alkenes via transient diazo intermediates. This process suggested to proceed through the formation of either carbenium ion (in aprotic solvents) or carbene (in protic solvents) intermediates (Figure 1).…”

“…1457) published since 2000 (Figure 3). Moreover, most of the advances in the carbene chemistry of N ‐sulfonyl hydrazone have been highlighted in numerous reviews, [ 10‐19,28‐29 ] book chapters, [ 18 ] and personal Accounts. [ 27,30 ] The prime objective of this review is to showcase the key achievements in the carbene chemistry of N ‐sulfonyl hydrazones over the past two decades.…”

Cyclic diaryliodonium salts: applications and overview

“…The anion attached with cyclic iodonium salt can be changed through another anion via ion-exchange reactions using the appropriate source of desired anions. The five or sixmembered cyclic diaryliodonium salts can be used for synthesizing many heterocycles 52,53 having different properties. Polycyclic and complicated heterocycles compounds like tribenzo azepine, dibenzo quinoline, triphenylene, acridanes, diarylmethane amides, dibenzoquinolines, dibenzotellurophenes aryl-imidazole and dibenzofurans which were difficultly prepared in conventional methods, are easily synthesized using cyclic iodonium salts (Fig.…”