Cobalt-catalyzed arylation and alkenylation of alpha-bromo eneformamides and enecarbamates by cross-coupling with organic bromides: Application to the synthesis of functionalized piperidines and azepanes

• C2 arylation/alkenylation of α-bromo enamides is reported.
• Two ‘vinyl’ bromides reductively couple under cobalt catalysis.
• The bite angle of the cobalt-bound phosphine ligand is critical.
• This umpolung reactivity mode affords versatile piperidines/azepanes.
• The synthetic utility of the products is subsequently exemplified.

The synthesis of α-arylated and alkenylated piperidine and azepane derivatives has been accomplished through cross-coupling of α-bromo eneformamides or enecarbamates with feedstock organic halides such as aryl and vinyl bromides, under cobalt catalysis. The coupling products, which themselves are synthetic intermediates for accessing other functionalized piperidines and azepanes are obtained in good to excellent yields.

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