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A novel, metal-free, and regioselective approach for the synthesis of isoxazoline/cyclic nitrone-featured methylenes has been developed by the reaction of readily accessible β,γ- and γ,d-unsaturated ketoximes with TEMPO via tandem iminoxyl radical-promoted cyclization/TEMPO-mediated Cope-like elimination, respectively. This protocol utilizes commercially available TEMPO as the iminoxyl radical initiator as well as the β-hydrogen acceptor in the Cope-like elimination. [ABSTRACT FROM AUTHOR]

DFT calculations have been carried out to investigate the reaction mechanism for PdII-mediated enantioselective C-H iodination. Iodination of the aryl ortho C-H bond of benzylamines catalyzed by PdII diacetate complexes in the presence of the L-MPAA ligand experiences three main steps: first, C-H bond activation; second, oxidative addition of iodine on PdII and reductive elimination of iodobenzene; third, catalyst regeneration through ligand exchange. The C-H bond activation is found to be the rate-determining step of the overall iodination due to higher activation energy. The reaction barrier for the formation of iodinated (R)-benzylamine is lower than that of (S)-benzylamine, which confirms the R enantioselectivity in iodination at room temperature. The retainment of the coordination of one acetic acid on PdII and the chelating MPAA ligand during the catalyzed reaction are suggested to give space economy to facilitate the C-H bond activation. The NHTf functional group on the substrate is found to be very important for ortho C-H iodination at ambient condition. Our calculated results are consistent with the experimental observations. [ABSTRACT FROM AUTHOR]

The intramolecular addition of hydrazone radicals to carbon-carbon double bonds was achieved by using TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) or DIAD (diisopropyl azodicarboxylate) as the hydrazone radical initiator as well as the carbon radical scavenger. Consequently, alkenes were difunctionalized to afford pyrazolines and tetrahydropyridazines via C-N forming 5-exo-trig and 6-exo-trig cyclizations, respectively, and allyls were trifunctionalized to afford pyrazolines via C-N forming tandem 1,5-H-shift/5-exo-trig cyclizations under metal-free neutral conditions. [ABSTRACT FROM AUTHOR]

The Cu/N-ligand/TEMPO catalytic system was first applied to the aerobic oxidative synthesis of heterocycles. As demonstrated, 2-substituted quinazolines and 4H-3,1-benzoxazines were synthesized efficiently from the one-pot reaction of aldehydes with 2-aminobenzylamines and 2-aminobenzyl alcohols, respectively, by employing CuCl/DABCO/4-HO-TEMPO as the catalysts and oxygen as the terminal oxidant. [ABSTRACT FROM AUTHOR]