β-Lactams are important scaffolds in drug design
and frequently used as reactive intermediates in organic synthesis.
Catalytic reactions featuring intramolecular C–H amidation
of alkyl carboxamide substrates could provide a straightforward disconnection
strategy for β-lactam synthesis. Herein, we report a streamlined
method for asymmetric synthesis of β-aryl β-lactams from
propanoic acid and aryl iodides via Pd-catalyzed sequential C(sp3)–H functionalization. The lactam-forming reaction
provides an example of PdII-catalyzed enantioselective
intramolecular C(sp3)–H amidation reaction and proceeds
up to 94% ee. The use of a 2-methoxy-5-chlorophenyl iodide oxidant
is critical to control the competing reductive elimination pathways
of the PdIV intermediate to achieve the desired chemoselectivity.
Mechanistic studies suggest that both steric and electronic effects
of the unconventional aryl iodide oxidant are responsible for controlling
the competing C–N versus C–C reductive elimination pathways
of the PdIV intermediate.
A new
protocol for amide-directed Cu-catalyzed aminoalkylation
of unactivated alkenes using cyclobutanone oxime esters as alkyl radical
donors is developed. Both primary and secondary alkyl groups can be
selectively installed at the C4 position of terminal or cis-internal 3-alkenamides in moderate to good yield. This reaction
offers a useful method for the diastereoselective synthesis of β-lactams
bearing 4-cyanoalkyl β-substituents. The use of a weakly coordinating
counteranion as the Cu catalyst is critical for the formation of β-lactam
products.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.