Ru-Catalyzed Site-Selective Aliphatic C–H Bond Silylation of Amides and Carbamides

Abstract

Hydrido ruthenium complexes (POCNP)­RuH­(NBD) (NBD = norbornadiene) supported by N/O-bridged pincer ligands have been synthesized and characterized. The Ru complex containing a pincer ligand with an indolol scaffold exhibits high catalytic activity for the intermolecular aliphatic C–H bond silylation of amides and carbamides. The reaction proceeds selectively at the C–H bonds adjacent to the nitrogen atom to efficiently afford α-silyl amides and carbamides.

Iridium(iii) bis(thiophosphinite) pincer complexes: synthesis, ligand activation and applications in catalysis

“…We would like to note that pincer systems are typically considered as robust and in fact, such ligands often engage in cooperative reactivities with metal centres. Activation of monoanionic PCP type ligands is unknown for the well-established R POCOP R 2a and R PNCEP R (E = O, S) 8 a ,22 complexes and was so far only observed for R PSCSP R systems. 13…”

A Journey from June 2018 to October 2021 with N,N-Dimethylformamide and N,N-Dimethylacetamide as Reactants

“…The above reactions involve radical intermediates I 9 and/or I 4 . Borylation [130][131][132], silylation [133], and amidation [134] of N-adjacent C-H bond of DMAc have been achieved with bis(pinacolato)diboron and Rh or Ir catalysis (Scheme 41a,b), triethylsilyl hydride, Ru catalysis, and tert-butylethylene as the hydrogen acceptor (Scheme 41c), and N-haloimides under blue light irradiation (Scheme 41d). The transition-metal catalysis could involve the C(sp 3 )−H bond oxidative addition to the metal center [135,136] while the photochemical conditions promote the formation of radical I 9 [134].…”

Breaking Conventional Site Selectivity in C–H Bond Activation: Selective sp3 versus sp2 Silylation by a Pincer-Based Pocket

“…The intramolecular version of this transformation provides a straightforward approach to Si-containing heterocycles, which are not naturally occurring, but have demonstrated importance in drug discovery and material sciences . While most known intramolecular C­(sp 3 )–H silylation reactions involved benzylic C–H bonds and moderately activated C­(sp 3 )–H bonds attached to heteroatoms, a few disclosed the silylations of unactivated δ-C–H bonds (δ to the Si atom) in alkyl chains to form five-membered Si-containing heterocyle cyclopentane. , Surveying these examples reveal that none of the catalysts effect selective silylation of unactivated δ-C­(sp 3 )–H over spatially and geometrically unbiased ortho δ-C­(sp 2 )–H bonds. For a closely related example, Gevorgyan and co-workers reported [Ir­(COD)­OMe] 2 -catalyzed primary δ-C­(sp 3 )–H silylation in tertiary silanes bearing a picolyl auxiliary group, which plays a key role in promoting the C–H bond cleavage by stabilizing a 6-membered iridacycle intermediate.…”