The Pd‐catalyzed coupling of aryl (pseudo)halides and amines is one of the most powerful approaches for the formation of C(sp2)−N bonds. The pioneering reports from Migita and subsequently Buchwald and Hartwig on the coupling of aminostannanes and aryl bromides rapidly evolved into general and practical tin‐free protocols with broad substrate scope, which led to the establishment of what is now known as the Buchwald–Hartwig amination. This Minireview summarizes the evolution of this cross‐coupling reaction over the course of the past 25 years and illustrates some of the most recent applications of this well‐established methodology.
A rhodium-catalyzed regio- and enantioselective intermolecular allylation of malononitriles as masked acyl cyanides (MAC) with terminal and symmetrical internal allenes is reported. A Rh /Josiphos catalytic system combined with subsequent oxidative degradation of the primary adducts enables a straightforward access to α-branched, β,γ-unsaturated carbonyl compounds. The present protocol exhibits perfect atom economy in the allylation step and is characterized by a great functional group compatibility. Furthermore, the use of α-substituted malononitriles allowed for the construction of all-carbon quaternary centers.
A highly efficient rhodium-catalyzed chemo- and regioselective addition of β-ketoacids to alkynes is reported. Applying a Rh(i)/(S,S)-DIOP catalyst system, γ,δ-unsaturated ketones were prepared with exclusively branched selectivity under mild conditions. This demonstrates that readily available alkynes can be an alternative entry to allyl electrophiles in transition-metal catalyzed allylic alkylation reactions.
Figure 1. Selected tetrahydrocarbazole (THC) natural products and structurally related alkaloids. Scheme 1. Transition-Metal Catalyzed Strategies for the Synthesis of Enantioenriched 1-Vinyltetra-hydrocarbazoles Letter pubs.acs.org/OrgLett
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