Chapter Two - Recent Advances in Transition-Metal-Catalyzed Cross-Coupling Reactions With N-Tosylhydrazones

Add time:09/10/2019    Source:sciencedirect.com

Transition-metal-catalyzed cross-coupling reactions have experienced considerable growth in the past decades. These reactions have proved to be powerful tools for assembling structurally complex molecules for use in applications ranging from medicines to materials. Among these transformations, catalytic coupling reactions of readily available substrates of N-tosylhydrazones, which can be conveniently accessed by the condensation of carbonyl compounds with N-tosylhydrazine, have provided a novel and superior avenue toward the syntheses of functionalized molecules and efficient construction of carbon–carbon and carbon–heteroatom bonds. As particular examples, this coupling strategy from N-tosylhydrazones as substrates enables the concise preparation of substituted alkenes as well as various heterocycle scaffolds.Transition-metal-catalyzed carbene-coupling reactions not only introduce the cross-coupling strategy in carbene chemistry, but more importantly, it represents a paradigm shift in the area. Therefore, for this approach to be generally useful the exploration of stable and effective carbene precursors has become a crucial topic. As stable and easily accessible surrogates for diazo compounds, N-tosylhydrazones can generate diazo intermediates in situ in the presence of a base. It is worth noting that this process is regarded as a diazo compound slow-release methodology, which suppresses the self-coupling of diazo groups, thus greatly benefiting the reaction (vide infra). By employing N-tosylhydrazones as the available reaction partners, transition-metal-catalyzed carbene-coupling reactions demonstrate practical and convenient usefulness in synthetic chemistry and other fields.This chapter aims to describe the recent advances of transition-metal-catalyzed cross-coupling reactions with N-tosylhydrazones, especially those involving migratory insertion of a metal-carbene intermediate. In this content, we will introduce these transformations according to different transition-metal catalysts, demonstrating the superiority and generality of N-tosylhydrazones as novel cross-coupling partners in transition-metal-catalyzed cross-coupling reactions.

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