The
generation of aminium radical cation species from N-nitrosoamines is disclosed for the first time through visible-light
excitation at 453 nm. The developed visible-light-promoted photoaddition
reaction of N-nitrosoamines to alkenes was combined
with the o-NQ-catalyzed aerobic oxidation protocol
of amines to telescope the direct handling of harmful N-nitroso compounds, where the desired α-amino oxime derivatives
were obtained in a one-pot tandem N-nitrosation and photoaddition
sequence.
Aryl-secondary alkyl cross-coupling with aryl sulfonate esters as coupling partners remains a significant challenge. Efficient cross-coupling between aryl/alkenyl triflates and acyclic secondary alkylboronic acids is realized for the first time to provide a series of sterically congested acyclic secondary alkyl arenes/olefins in good to excellent yields. The employment of sterically bulky P,P[double bond, length as m-dash]O ligand L1/L2 is crucial for the high yields and selectivities. The method has enabled a concise and 4-step synthesis of a key intermediate of male contraceptive agent and PAF antagonist gossypol.
A biomimetic
alcohol dehydrogenase (ADH)-like oxidation protocol
was developed using an ortho-naphthoquinone catalyst
in the presence of a catalytic amount of base. The developed organocatalytic
aerobic oxidation protocol proceeds through the intramolecular 1,5-hydrogen
atom transfer of naphthalene alkoxide intermediates, a mechanistically
distinctive feature from the previous alcohol dehydrogenase mimics
that require metals in the active form of catalysts. The ADH-like
aerobic oxidation protocol should provide green alternatives to the
existing stoichiometric and metal-catalyzed alcohol oxidation reactions.
The nitroso group served as a traceless directing group for the C−H functionalization of N-alkylanilines, ultimately removed after functioning either as an internal oxidant or under subsequent reducing conditions. The unique ability of o-NQ catalysts to aerobically oxidize the N-alkylanilines without using solvents and stoichiometric amounts of oxidants has rendered the new opportunity to develop the telescoped catalyst systems without a need for directly handling the hazardous Nnitroso compounds.
Biomimetic oxidation of primary amines to carboxylic acids has been developed where the copper‐containing amine oxidase (CuAO)‐like o‐NQ‐catalyzed aerobic oxidation was combined with the aldehyde dehydrogenase (ALDH)‐like TBHP‐mediated imine oxidation protocol. Notably, the current tandem oxidation strategy provides a new mechanistic insight into the imine intermediate and the seemingly simple TBHP‐mediated oxidation pathways of imines. The developed metal‐free amine oxidation protocol allows the use of molecular oxygen and TBHP, safe forms of oxidant that may appeal to the industrial application.
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