6724-71-6Relevant articles and documents
Catalytic C-N Bond-Forming Reactions Enabled by Proton-Coupled Electron Transfer Activation of Amide N-H Bonds
Nguyen, Lucas Q.,Knowles, Robert R.
, p. 2894 - 2903 (2016)
Over the past three years, our group has become interested in the ability of proton-coupled electron transfer (PCET) to facilitate direct homolytic bond activations of common organic functional groups that are challenging substrates for conventional hydro
Extended Hydrogen Bond Networks for Effective Proton-Coupled Electron Transfer (PCET) Reactions: The Unexpected Role of Thiophenol and Its Acidic Channel in Photocatalytic Hydroamidations
Berg, Nele,Bergwinkl, Sebastian,Nuernberger, Patrick,Horinek, Dominik,Gschwind, Ruth M.
supporting information, p. 724 - 735 (2021/02/01)
Preorganization and aggregation in photoredox catalysis can significantly affect reactivities or selectivities but are often neglected in synthetic and mechanistic studies, since the averaging effect of flexible ensembles can effectively hide the key activation signatures. In addition, aggregation effects are often overlooked due to highly diluted samples used in many UV studies. One prominent example is Knowles's acceleration effect of thiophenol in proton-coupled electron transfer mediated hydroamidations, for which mainly radical properties were discussed. Here, cooperative reactivity enhancements of thiophenol/disulfide mixtures reveal the importance of H-bond networks. For the first time an in-depth NMR spectroscopic aggregation and H-bond analysis of donor and acceptor combined with MD simulations was performed revealing that thiophenol acts also as an acid. The formed phosphate-H+-phosphate dimers provide an extended H-bond network with amides allowing a productive regeneration of the photocatalyst to become effective. The radical and acidic properties of PhSH were substituted by Ph2S2 and phosphoric acid. This provides a handle for optimization of radical and ionic channels and yields accelerations up to 1 order of magnitude under synthetic conditions. Reaction profiles with different light intensities unveil photogenerated amidyl radical reservoirs lasting over minutes, substantiating the positive effect of the H-bond network prior to radical cyclization. We expect the presented concepts of effective activation via H-bond networks and the reactivity improvement via the separation of ionic and radical channels to be generally applicable in photoredox catalysis. In addition, this study shows that control of aggregates and ensembles will be a key to future photocatalysis.
Reductive amination of levulinic acid to N-substituted pyrrolidones over RuCl3 metal ion anchored in ionic liquid immobilized on graphene oxide
Raut, Amol B.,Shende, Vaishali S.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
, p. 206 - 214 (2020/02/15)
Reductive amination of biomass derived Levulinic acid (LA) for the synthesis of N-substituted pyrrolidones is one of the highly attractive routes for biomass valorization. The supported homogeneous metal precursor into the solid surface is an important context in the field of catalysis because these types of catalysts provide the heterogeneous nature and meet the needs of recyclability. Herein, we have reported a synthesis of catalyst with ruthenium ion supported on ionic liquid immobilized into graphene oxide (Ru?GOIL) and its application for reductive amination reaction. Synthesized catalyst is characterized using different analytical techniques such as FT-IR, XRD, XPS, TGA, FEG-SEM, TEM and EXAFS analysis. The prepared Ru?GOIL found to be highly effective for reductive amination of LA and under these optimized conditions various N-substituted pyrrolidones derivatives were synthesized in excellent yield (78–93%). Ru?GOIL catalyst demonstrated great catalytic performance for reductive amination reaction of LA giving good turnover frequency (TOF = 62 h?1) value in comparison with other catalysts. The Ru?GOIL catalyst was recycled for six reaction runs with slight drop-in activity after 4th cycle. Practical applicability of the developed catalyst was successfully demonstrated by direct transformation of biomass waste (rice husk and wheat straw) derived LA to N-substituted pyrrolidones.
