Ruthenium-Catalyzed Oxidative C–H Bond Alkenylations in Water: Expedient Synthesis of Annulated Lactones

Abstract

Ruthenium-catalyzed cross-dehydrogenative C-H bond alkenylations occurred efficiently in environmentally benign water, which was exploited for an oxidative phthalide synthesis with ample scope. Mechanistic studies provided strong evidence for the oxidative alkenylation to proceed by an irreversible C-H bond metalation via acetate assistance.

Conformation-induced remote meta-C–H activation of amines

“…In this context, the activation of C–H bonds 5 or 6 bonds away from a functional group via cyclometalation has been extensively studied. 1-13 However, directed activation of C–H bonds that are distal (>6 bonds away) from functional groups has remained difficult, especially when the target C–H bonds are geometrically inaccessible through directed metalation due to the ring strain encountered in cyclometalation. 14,15 Herein we report a recyclable template that directs the olefination and acetoxyation of distal meta -C–H bonds (as far as 11 bonds away) of anilines and benzylic amines.…”

“…1 In analogy to the principles of proximity-driven metalation, 2 this type of methodology enables the selective functionalization of C–H bonds that are 5–6 bonds away from the directing atom through cyclometalation. 3-13 While this approach has enabled the discovery of numerous transformations over the past decade, the functionalization of C–H bonds that are located farther away from the coordinating functional group remains a largely unsolved problem in organic synthesis, especially when their locations do not permit cyclometalation due to geometric strain. 14-18 …”

Ruthenium‐Catalyzed Synthesis of Heterocycles via CH Bond Activation

“…Following the oxidative C-H bond alkenylation reaction, subsequent intramolecular oxa-Michael reaction occurred leading to phthalides in good yields (Eq. (7.12)) [18]. The reactions took place with water as an environmentally benign medium under mild conditions.…”

Ligand-enabled cross-coupling of C(sp3)–H bonds with arylboron reagents via Pd(II)/Pd(0) catalysis

“…Transition metal-catalyzed C–H activation directed by heteroatom directing groups has rapidly emerged as a fertile field for developing a diverse range of catalytic carbon–carbon and carbon–heteroatom bond forming reactions 1–10 . During our efforts towards the development of Pd(II)-catalyzed C–H activation reactions using a broad range of synthetically useful substrates, it has become evident that controlling the reactivity and selectivity of catalysts through the use of external ligands such as amino acids 11–16 , pyridines, and quinolines 17,18 is crucial for realizing their full potential as useful tools for synthesis.…”