Rather
surprisingly, C–C bond formation through “intermolecular”
radical addition to internal ynamides has never been reported. Actually,
ynamides are excellent acceptors for “electrophilic”
carbon-centered radicals. These processes enable the introduction
of functionalized alkyl chains at Cβ, groups that have not yet
been introduced via the addition of organometallics. Radical carboiodination
affords persubstituted α-iodo-enamides in moderate to high yield.
The addition is totally stereoselective. Theoretical support to the
mechanism and the scope and limitation of the reaction are discussed.
An efficient catalytic preparation of synthetically useful new β‐borylated enamides was achieved under relatively mild conditions via a regioselective iridium‐catalyzed C(sp2)−H borylation. The method features broad substrate scope, good functional group tolerance and efficient scale‐up. These C‐3 borylated enamides can be advantageously exploited in cross‐coupling reactions and converted into valuable 3,3‐dihalogeno‐2‐methoxypiperidines in very short reaction times.
Mn(OAc) 3 /Cu(OAc) 2 -mediated reaction between ynamides, derived from oxazolidone or 3-methylindole carboxylate, and cyclic α-dicarbonyl radicals led to the one-pot synthesis of 2aminofurans. The transformation involves addition of the α-dicarbonyl radical to ynamide, oxidation to ketene-iminium, and polar cyclization steps to provide original persubstituted 2-aminofurans in good to excellent yields. This work represents the first radical route for the synthesis of furans from ynamides.
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