A ruthenium/C-TunePhos catalytic system has been identified for highly efficient direct reductive amination of simple ketones. The strategy makes use of ammonium acetate as the amine source and H as the reductant and is a user-friendly and operatively simple access to industrially relevant primary amines. Excellent enantiocontrol (>90% ee for most cases) was achieved with a wide range of alkyl aryl ketones. The practicability of this methodology has been highlighted by scalable synthesis of key intermediates of three drug molecules. Moreover, an improved synthetic route to the optimal diphosphine ligand C-TunePhos is also presented.
A series of modular and rich electronic tridentate ferrocene aminophosphoxazoline ligands (f-amphox) have been successfully developed and used in iridium-catalytic asymmetric hydrogenation of simple ketones to afford corresponding enantiomerically enriched alcohols under mild conditions with superb activities and excellent enantioselectivities (up to 1 000 000 TON, almost all products up to >99% ee, full conversion). The resulting chiral alcohols and their derivatives are important intermediates in pharmaceuticals.
The catalytic generation of hypervalent iodine(III) reagents by anodic electrooxidation was orchestrated towards an unprecedented electrocatalytic C−H oxygenation of weakly coordinating aromatic amides and ketones. Thus, catalytic quantities of iodoarenes in concert with catalytic amounts of ruthenium(II) complexes set the stage for versatile C−H activations with ample scope and high functional group tolerance. Detailed mechanistic studies by experiment and computation substantiate the role of the iodoarene as the electrochemically relevant species towards C−H oxygenations with electricity as a sustainable oxidant and molecular hydrogen as the sole by‐product. para‐Selective C−H oxygenations likewise proved viable in the absence of directing groups.
A new tetradentate ruthenium complex has been developed for hydrogenation of esters. The catalyst's structure features a pyridinemethanamino group and three tight chelating five-membered rings. The structure character is believed to be responsible for its high stability and high carbonylation-resistant properties. Thus, this catalyst shows outstanding performance in the catalytic hydrogenation of a variety of esters, especially for fatty acid esters, which may be used in practical applications. New insight on designing hydrogenation catalyst for reducing esters to alcohols has been provided through theoretical calculations.
Lactams with a stereogenic
center adjacent to the N atom have existed
in many medicinal agents and bioactive alkaloids. Herein we report
a broadly applicable synthesis of enantioenriched NH lactams through
a one-pot asymmetric reductive amination/cyclization sequence of easily
available keto acids/esters. Such cascade processes alleviate the
demand for protecting group manipulations as well as intermediate
purification. This strategy is capable of constructing enantioenriched
lactams and benzo-lactams of a five-, six-, or seven-membered ring
in generally high yield and with excellent enantioselectivities (up
to 97% ee). Scalable and concise syntheses of key drug intermediates
have further displayed the importance of this methodology.
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