Oxygenation Of Arenes Research Articles

Photoinduced meta-Selective C-H Oxygenation of Arenes.

The merger of photocatalysis and transition-metal catalysis has recently emerged as an adaptable platform for the development of innovative and environmentally benign synthetic methodologies. In contrast to classical transformation by Pd complexes, photoredox Pd catalysis operates through a radical pathway in the absence of a radical initiator. Using the synergistic merger of photoredox and Pd catalysis, we have developed a highly efficient, regioselective, and general meta-oxygenation protocol for diverse arenes under mild reaction conditions. The protocol showcases the meta-oxygenation of phenylacetic acids and biphenyl carboxylic acids/alcohols and is also amenable for a series of sulfonyls and phosphonyl-tethered arenes, irrespective of the nature and position of the substituents. Unlike thermal C-H acetoxylation which operates through the PdII/PdIV catalytic cycle, this metallaphotocatalytic C-H activation involves PdII/PdIII/PdIV intermediacy. The radical nature of the protocol is established through radical quenching experiments and EPR analysis of the reaction mixture. Furthermore, the catalytic path of this photoinduced transformation is established through control reactions, absorption spectroscopy, luminescence quenching, and kinetic studies.

Catalytic Site-Selective C–H Oxygenation of Arenes

Catalytic Site-Selective C–H Oxygenation of Arenes

A PdII Carbene Complex with Anthracene Side‐Arms for π‐Stacking on Reduced Graphene Oxide (rGO): Activity towards Undirected C–H Oxygenation of Arenes

An N‐heterocyclic carbene palladium(II) complex containing two anthracene side arms was immobilized on the surface of reduced graphene oxide (rGO) by π‐stacking. The activity of the homogeneous analogue and the supported complex in undirected C–H acetoxylation reaction of arenes was studied. The results show that the catalytic efficiency in acetoxylation of benzene is improved in the immobilized materials compared to the homogeneous analogue. According to XPS analysis, the immobilized catalyst maintains the original oxidation state of PdII after the catalytic reaction.

Triazole-Directed Pd-Catalyzed C(sp(2))-H Oxygenation of Arenes and Alkenes.

Selective Pd-catalyzed C(sp(2))-H oxygenation of 4-substituted 1,2,3-triazoles is described. Unlike previous metal-catalyzed C-H functionalization events, which preferentially occur at the activated heterocyclic C-H bond, the regioselective oxygenation of the arene/alkene moiety is now achieved featuring the unconventional role of a simple triazole scaffold as a modular and selective directing group.

Pd-Catalyzed Double Oxygenation of Arenes with PyrDipSi as Directing Group

Pd-Catalyzed Double Oxygenation of Arenes with PyrDipSi as Directing Group

Double-fold C-H oxygenation of arenes using PyrDipSi: a general and efficient traceless/modifiable silicon-tethered directing group.

The efficient Pd-catalyzed double-fold C-H oxygenation of arenes into resorcinols using the newly developed 2-pyrimidyldiisopropylsilyl (PyrDipSi) directing group is described. Its use allows for the sequential introduction of OAc and OPiv groups in a one-pot manner to produce orthogonally protected resorcinol derivatives. The PyrDipSi group is superior to the previously developed 2-pyridyldiisopropylsilyl (PyDipSi) group, as it is efficient for monooxygenation of ortho-substituted arenes. Notably, the PyrDipSi group can be easily installed into arene molecules and can be easily removed or modified after the oxygenation reaction.

Back Cover: Remarkably High Reactivity of Pd(OAc)2/Pyridine Catalysts: Nondirected CH Oxygenation of Arenes (Angew. Chem. Int. Ed. 40/2011)

Back Cover: Remarkably High Reactivity of Pd(OAc)2/Pyridine Catalysts: Nondirected CH Oxygenation of Arenes (Angew. Chem. Int. Ed. 40/2011)

Remarkably High Reactivity of Pd(OAc)2/Pyridine Catalysts: Nondirected CH Oxygenation of Arenes

Less is more: The rational optimization and general applicability of the catalytic system Pd(OAc)2/pyridine is described (see scheme). The catalyst shows excellent reactivity in the CH oxygenation of simple aromatic substrates. The Pd/pyridine ratio is critical as the use of one equivalent of pyridine per Pd center leads to dramatic enhancements in both reactivity and site selectivity in comparison to Pd(OAc)2 alone.

Remarkably High Reactivity of Pd(OAc)2/Pyridine Catalysts: Nondirected CH Oxygenation of Arenes

Remarkably High Reactivity of Pd(OAc)₂/Pyridine Catalysts: Nondirected CH Oxygenation of Arenes

Synthesis of fine chemicals by the use of oxidation. Oxygenation of arenes with hydrogen peroxide.

Etude de la synthese de p-benzoquinones par oxydation de benzaldehydes ou de benzenes en phenols puis en quinones