Investigation of Stepwise and Stoichiometric Palladium-Mediated ortho-C–H Bond Arylation and Alkylation of 9(10H)-Acridinone

Abstract

We present a stoichiometric methodology for the synthesis of 4-arylated/alkylated 9­(10H)-acridinones via a palladium-mediated ortho-C–H bond activation and C–C bond cross-coupling strategy. In the reaction, a N-(pyridin-2-yl)-9­(10H)-acridinone palladacycle was employed as the starting substrate, which could be readily prepared by the stoichiometric reaction of N-(pyridin-2-yl)-9­(10H)-acridinone and palladium­(II) acetate in 89% isolated yield. Meanwhile, potassium aryl/alkyltrifluoroborates and p-benzoquinone were introduced to serve as the coupling partner and reaction promoter, respectively, in the presented palladium-mediated ortho-C–H bond arylation/alkylation of 9­(10H)-acridinone. The reaction eventually furnished a variety of 4-arylated/alkylated 9­(10H)-acridinones in 31–95% yields. The structures of N-(pyridin-2-yl)-9­(10H)-acridinone palladacycle substrate and 4-phenylated/cyclopropylated 9­(10H)-acridinone products were elucidated by X-ray crystallography. Kinetic isotope effect studies, as well as controlled experiments, were carried out to gain insight into the reaction mechanism. Finally, the removal of the directing group (i.e., pyridin-2-yl) was demonstrated on one of the ortho-arylated products, 4-phenyl-N-(pyridin-2-yl)-9­(10H)-acridinone.

MOF‐Stabilized Perfluorinated Palladium Cages Catalyze the Additive‐Free Aerobic Oxidation of Aliphatic Alcohols to Acids

“…The corners of the [Pd II 6 ( μ ‐HOAc) 2 (H 2 O) 12 (L 3 ) 4 ] cages can be located on [Pd II 2 ( μ ‐HOAc)(H 2 O) 2 ] dimeric fragments, which reside at the sides of the elliptic assembly (Figures S2–S3) and interact with the MOF by means of water‐mediated H‐bonds. Each Pd(II) exhibits regular square planar geometry, with Pd−N [2.13(2) and 2.077(11) Å for Pd‐N L3 and 2.070(10) Å for detected Pd‐NH 3 , respectively], Pd‐OH 2 [2.35(2) and 2.30(2) Å for detected Pd‐OH 2 ] and Pd‐OAc [2.34(2) Å] bond distances similar, or longer for the latter, to those found in the literature [74] . Figure 3c shows that Pd(II) separations through AcOH and L 3 bridges are 6.96(1) and 13.63(1) Å, respectively.…”

“…Each Pd(II) exhibits regular square planar geometry, with PdÀ N [2.13(2) and 2.077(11) Å for Pd-N L3 and 2.070(10) Å for detected Pd-NH 3 , respectively], Pd-OH 2 [2.35(2) and 2.30(2) Å for detected Pd-OH 2 ] and Pd-OAc [2.34(2) Å] bond distances similar, or longer for the latter, to those found in the literature. [74] Figure 3c shows that Pd(II) separations through AcOH and L 3 bridges are 6.96(1) and 13.63 S3c). The synergic stabilizations, ensured by a such MOF, allow the framework to act as impeccable platform to efficiently safeguard the robustness of the assembled cages, which in turn exhibit high activity in heterogeneous metalbased supramolecular catalysis (see below).…”

Synthesis and Mechanistic Investigation of Bipyrazolo[1,5-a]pyridines via Palladium-Catalyzed Cross-Dehydrogenative Coupling of Pyrazolo[1,5-a]pyridines

“…The conventional syntheses of pyrazolo­[1,5- a ]­pyridines usually involve the [3 + 2] cyclization reactions of prefunctionalized aminopyridines and alkynes (or alkenes), which are not only tedious but also generate excess chemical wastes. To bypass their low synthetic efficiency and atom economy, our research groups have investigated alternative C–H bond activation strategies , to produce novel pyrazolo­[1,5- a ]­pyridine derivatives. In 2016, one of us successfully developed a palladium-catalyzed direct C–H bond arylation methodology that facilitates the functionalization of the parental pyrazolo­[1,5- a ]­pyridine substrate at the C(3)- and C(7)-positions.…”