Palladium‐Catalyzed Domino Process to Construct 2,3,9,9a‐Tetrahydro‐1H‐Fluorene Derivatives:Transient σ‐Alkylpalladium(II) Complex Mediated C(sp²)‐H Bond Activation

Abstract

A palladium‐catalyzed cascade reaction involving domino Heck/intramolecular C−H arylation to construct 2,3,9,9a‐tetrahydro‐1H‐fluorene derivatives was developed. Products are obtained in moderate to excellent yields. The transient σ‐alkylpalladium(II) complex is the key intermediate, which mediates the C(sp2)‐H bond activation via a six‐metallacycle. According to a transient σ‐alkylpalladium(II) complex, the control experiment demonstrates that β‐H elimination is faster than C−H activation. The methodology shows high chemoselectivity and good functional group tolerance.

Transition‐Metal‐Catalyzed Cyclization of Alkenyl Iodide

“…This strategy showed excellent chemoselectivity and acceptable functional group tolerance with medium to excellent yields (Scheme 12). [45] …”

“…This strategy showed excellent chemoselectivity and acceptable functional group tolerance with medium to excellent yields (Scheme 12). [45] A possible reaction mechanism is shown in Scheme oxidative addition of alkyl iodide might not be eliminated though intermediate 60 is not detected during the reaction. Subsequently, the CÀ H bond activation of the transient σ-alkyl Pd II complex generates a six-metallacycle 61 via a concerted metalation-deprotonation process.…”

Highly diastereoselective synthesis of an octahydro-1H-cyclpenta[c]pyridine skeleton via a Pd/Au-relay catalyzed reaction of (Z)-1-iodo-1,6-diene and alkyne

“…There has been increasing attention to the synthesis of incarvillateine ( 2 ), such as the Suh group 2 and the Jia group, 3 who synthesized incarvillateine in 14 and 9 steps, respectively (Scheme 1a and b). Up to now, our group has developed several strategies in the construction of piperidine derivates via transition metal catalysis, 4 which inspires us to design a new route to achieve the bicyclic octahydro-1 H -cyclopenta[ c ]pyridine scaffold for the incarvilline skeleton. As shown in Scheme 1c, we propose that bicyclic piperidine scaffold A could be achieved via an intramolecular cyclization of 1,5-enynes B because 1,5-enynes have unique advantages in building five-membered rings.…”