An atom-economical strategy for the
C–H alkenylation and
C–H allylation of arenes by employing cyclopropenes as versatile
alkenylating and allylating reagents is reported, catalyzed by cobalt.
The Co-catalyzed C–H alkenylation process involves sequential
C–H and C–C bond cleavage. Under the optimized conditions,
broad-ranging alkenylated (hetero)arenes were synthesized with complete
(E)-stereoselectivity (up to 91%). The consecutive
C–H allylation proved viable under basic conditions via double-bond
migration of the initially generated alkenyl (hetero)arenes, thus
leading to allylated (hetero)arenes with high stereoselectivity of
olefin (E/Z ratio = 91:9 to 100:0).
A facile and efficient method for Cp*CoIII‐catalyzed C(sp2)–H bond alkylation was developed using 2‐aryl pyridines and unactivated alkenes. The reaction proceeded atom‐economically with readily available styrene derivatives and an abundant cobalt catalyst. This reaction tolerates a broad range of functional groups, directing groups, styrenes and affords mono‐diarylethane products with high linear selectivity. To demonstrate the synthetic utility and the potential application in organic synthesis, a gram‐scale reaction and further C–H bond functionalizations of the mono‐alkylated product were performed.
A simple transition metal-free strategy for the synthesis of pyrido[1,2-a]indolone derivatives has been devised through sodium methoxide-catalyzed intramolecular cyclization of 2-alkenylated N-pyrimidyl indoles. The reactions involved a Smiles rearrangement/cyclization cascade, which resulted in a new series of N-fused indoles, potentially applicable skeletons in medicinal chemistry. This reaction presents simple eco-friendly reaction conditions, a high atom-and cost-economy, a short reaction time, and a broad range of substrate scope with high reaction efficiency.
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