“…1a). Moreover, the cyclometallation concept has been remarkably expanded to positional selective C-H bond activation in arenes and alkanes 6–16 , but its utilization in site-selective C(alkenyl)-H bond functionalization still remains elusive 17–35 .Fig. 1Chelation-assisted olefinic C-H functionalization.…”
Great efforts have been made in the activation of a C(alkenyl)-H bond vicinal to the directing group to proceed via five- or six-membered endo-metallocycles. In stark contrast, functionalization of a C(alkenyl)-H bond geminal to the directing group via exo-metallocycle pathway continued to be elusive. Here we report the selective transformation of an olefinic C-H bond that is geminal to the directing group bearing valuable hydroxyl, carbamate or amide into a C-C bond, which proceeds through four- to eight-membered exo-palladacycles. Compared to the reported mechanisms proceeding only through six-membered exo-palladacycles via N,N-bidentate chelation, our weak and O-monodentate chelation-assisted C(alkenyl)-H activations tolerate longer or shorter distances between the olefinic C-H bonds and the coordinating groups, allowing for the functionalizations of many olefinic C-H bonds in alkenyl alcohols, carbamates and amides. The synthetic applicability has been demonstrated by the preparative scale and late-stage C-H functionalization of steroid and ricinoleate derivatives.
“…1a). Moreover, the cyclometallation concept has been remarkably expanded to positional selective C-H bond activation in arenes and alkanes 6–16 , but its utilization in site-selective C(alkenyl)-H bond functionalization still remains elusive 17–35 .Fig. 1Chelation-assisted olefinic C-H functionalization.…”
Great efforts have been made in the activation of a C(alkenyl)-H bond vicinal to the directing group to proceed via five- or six-membered endo-metallocycles. In stark contrast, functionalization of a C(alkenyl)-H bond geminal to the directing group via exo-metallocycle pathway continued to be elusive. Here we report the selective transformation of an olefinic C-H bond that is geminal to the directing group bearing valuable hydroxyl, carbamate or amide into a C-C bond, which proceeds through four- to eight-membered exo-palladacycles. Compared to the reported mechanisms proceeding only through six-membered exo-palladacycles via N,N-bidentate chelation, our weak and O-monodentate chelation-assisted C(alkenyl)-H activations tolerate longer or shorter distances between the olefinic C-H bonds and the coordinating groups, allowing for the functionalizations of many olefinic C-H bonds in alkenyl alcohols, carbamates and amides. The synthetic applicability has been demonstrated by the preparative scale and late-stage C-H functionalization of steroid and ricinoleate derivatives.
“… 1 However, this strategy has been applied much less frequently to non-aromatic heterocyclic scaffolds, 2 because vinylic C–H bonds are generally more challenging to functionalize than (hetero)aromatic C–H bonds. 3 Therefore, a method to assemble fused heterocyclic structures by vinylic C–H functionalization remains elusive. We focused on the palladium-catalyzed, norbornene (NBE)-mediated C–H functionalization reaction (the Catellani reaction).…”
In the presence of 5 mol% Pd(OAc)2, 1 equiv. of norbornene, and K2CO3, the reaction of 4-iodo-2-quinolones with tertiary o-bromobenzylic alcohols produced the desired benzopyran-fused 2-quinolones in moderate to high yields.
“…Despite the fact that formyl group holds a unique reactivity, its exploration in directed C−H bond activations is limited owing to its weak chelation ability and sensitive nature . In this context, the transient directing group (TDG) strategy has emerged as an excellent alternative for aldehydes since the pioneering work by Jun and co‐workers …”
Transition metal‐catalyzed ortho‐selective C(sp2)−H amidation of weakly coordinating aldehydes remains limited to precious metals such as Ir, Rh, Ru, etc. Herein, we put forward a novel report on ortho‐amidation of benzaldehydes employing user‐friendly dioxazolones under cost‐effective and air‐stable Cp*Co(III) catalysis. This catalytic transformation involves transient directing group strategy to enhance the ligating capability of weakly chelating aldehydes.
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.
