Intramolecular C(sp³)–H Bond Oxygenation by Transition‐Metal Acylnitrenoids

Abstract

This study demonstrates for the first time that easily accessible transition-metal acylnitrenoids can be used for controlled direct C(sp 3)-H oxygenations. Specifically, a ruthenium catalyst activates N-benzoyloxycarbamates as nitrene precursors towards regioselective intramolecular C À H oxygenations to provide cyclic carbonates, hydroxylated carbamates, or 1,2-diols. The method can be applied to the chemoselective CÀH oxygenation of benzylic, allylic, and propargylic C(sp 3)ÀH bonds. The reaction can be performed in an enantioselective fashion and switched in a catalyst-controlled fashion between C À H oxygenation and C À H amination. This work provides a new reaction mode for the regiocontrolled and stereocontrolled conversion of C(sp 3)-H into C(sp 3) À O bonds.

Multidimensional Screening Accelerates the Discovery of Rhodium Catalyst Systems for Selective Intra- and Intermolecular C–H Amidations

“…To evaluate the catalytic activity of the premised Cp*M­(LX)Cl complexes, group 9 metal precursors (Co, Rh, and Ir) and hydroxyquinoline derivatives ( L1 and L2 ) were simultaneously screened. On the other hand, as the nitrene precursors, we chose azidoformate ( 1a ), , N- benzoyloxycarbamate (1b ), − and N -tosyloxycarbamate ( 1c ), − which were fruitfully utilized for the catalytic C–H amination reactions to give 2-oxazolidinone 2 as a common product.…”

Nitrene‐Mediated C−H Oxygenation: Catalytic Enantioselective Formation of Five‐Membered Cyclic Organic Carbonates

“…Nitrene chemistry is traditionally used to incorporate nitrogen into a target molecule, either by nitrene addition to alkenes or by C−H amination [9] . In a recent surprising discovery, we found that nitrene chemistry can also be used as a tool to accomplish C(sp 3 )−H oxygenations (Figure 1b, upper reaction) [10] . The one‐step conversion of readily available alcohols to their corresponding N ‐benzoyloxycarbamates was followed by a ruthenium catalyzed formation of cyclic carbonates via the proposed intermediate formation of ruthenium nitrene species.…”

“…[9] In a recent surprising discovery, we found that nitrene chemistry can also be used as a tool to accomplish C(sp 3 )À H oxygenations (Figure 1b, upper reaction). [10] The one-step conversion of readily available alcohols to their corresponding N-benzoyloxycarbamates was followed by a ruthenium catalyzed formation of cyclic carbonates via the proposed intermediate formation of ruthenium nitrene species. However, unfortunately, this nitrene-mediated CÀ H oxygenation displayed critical drawbacks.…”

Catalysis with cycloruthenated complexes

“…Recently, Meggers and co-workers extended the use of this type of N-(2-pyridyl)NHC-derived ruthenium catalysts to C(sp 3 )-H activation of carbamates (Scheme 16). 46 Through a simple change in the substituents of the catalyst, they were able to attain C-N and C-O bond formation via nitrene and carbene insertions respectively. Since there was extensive literature precedent for ruthenium-catalysed nitrene insertions of carbamates, the authors focused instead on developing the C(sp 3 )-H oxygenation reaction to obtain cyclic carbonates.…”