MnO2 @Fe3 O4 Magnetic Nanoparticles as Efficient and Recyclable Heterogeneous Catalyst for Benzylic sp3 C-H Oxidation

Herein, we report a highly chemoselective and efficient heterogeneous MnO₂ @Fe₃ O₄ MNP catalyst for the oxidation of benzylic sp³ C-H group of ethers using TBHP as a green oxidant to afford ester derivatives in high yield under batch/continuous flow module. This catalyst was also effective for the benzylic sp³ C-H group of methylene derivatives to furnish the ketone in high yield which can be easily integrated into continuous flow condition for scale up. The catalyst is fully characterized by spectroscopic techniques and it was found that 0.424 % MnO₂ @Fe₃ O₄ catalyzes the reaction; the magnetic nanoparticles of this catalyst could be easily recovered from the reaction mixture. The recovered catalyst was recycled for twelve cycles without any loss of the catalytic activity. The advantages of MnO₂ @Fe₃ O₄ MNP are its catalytic activity, easy preparation, recovery, and recyclability, gram scale synthesis with a TOF of up to 14.93 h^-1 and low metal leaching during the reaction.

Iron-Catalyzed Oxyfunctionalization of Aliphatic Amines at Remote Benzylic C-H Sites

We report the development of an iron-catalyzed method for the selective oxyfunctionalization of benzylic C(sp(3))-H bonds in aliphatic amine substrates. This transformation is selective for benzylic C-H bonds that are remote (i.e., at least three carbons) from the amine functional group. High site selectivity is achieved by in situ protonation of the amine with trifluoroacetic acid, which deactivates more traditionally reactive C-H sites that are α to nitrogen. The scope and synthetic utility of this method are demonstrated via the synthesis and derivatization of a variety of amine-containing, biologically active molecules.

Stereoselective cascade reactions that incorporate a 7-exo acyl radical cyclization

[reaction: see text] Radical cascades that feature a 7-exo acyl radical cyclization followed by a 6-exo or 5-exo alkyl radical cyclization proceed with very good yields and diastereoselectivities. Two stereocenters are created by the reaction, and a single isomeric product was obtained from each of the five substrates examined. The relative configurations of the products are consistent with cyclizations occurring via chairlike or pseudochairlike transition states.

Bismuth-catalyzed benzylic oxidations with tert-butyl hydroperoxide

[reaction: see text] Oxidation of alkyl and cycloalkyl arenes with tert-butyl hydroperoxide catalyzed by bismuth and picolinic acid in pyridine and acetic acid gave the corresponding benzylic ketones (48-99%). Alternatively, oxidation of methyl arenes gave the corresponding substituted benzoic acids (50-95%). Preliminary mechanistic studies were consistent with a radical mechanism rather than a bismuth(III)-bismuth(V) cycle.