Direct Catalytic Access to N-Silylated Enamines from Enolizable Imines and Hydrosilanes by Base-Free Dehydrogenative SiN Coupling
作者:Julia Hermeke、Hendrik F. T. Klare、Martin Oestreich
DOI:10.1002/chem.201402866
日期:2014.7.21
α‐proton rather than α‐deprotonation of the enolizable imine followed by reaction with an electrophilic silicon reagent. The silicon electrophile, stabilized by a sulfur atom, is generated by cooperative activation of an SiH bond at the RuS bond of a tethered ruthenium(II) thiolate complex. After transfer of the silicon cation onto the imine nitrogen atom, the remaining ruthenium(II) hydride fulfills
Hidden Enantioselective Hydrogenation of N-Silyl Enamines and Silyl Enol Ethers in Net C═N and C═O Hydrosilylations Catalyzed by Ru–S Complexes with One Monodentate Chiral Phosphine Ligand
作者:Susanne Bähr、Martin Oestreich
DOI:10.1021/acs.organomet.7b00030
日期:2017.2.27
Ruthenium thiolate complexes with one chiral monodentate phosphine ligand are applied to enantioselective hydrosilylation of enolizable 'mines and ketones. The structural features of the catalyst exclude the presence of more than one phosphine ligand at the ruthenium center in the enantioselectivity-determining step. The enantiomeric excesses obtained in these reduction reactions ate moderate (up to 66% ee), but the stereochemical outcome enables an experimental analysis of the reaction pathways operative in this catalysis. A two-step sequence consisting of successive N-Si/O Si dehydrogenative coupling and enamine/enol ether hydrogenation is, the prevailing mechanisin Of action. Both steps involve cooperative bond activation at the Ru-S bond of the coordinatively unsaturated ruthenium complex: Si-H bond activation in the dehydrogenative coupling and heterolytic H-H splitting in the hydrogenation. Previously documented side reactions such as deprotonation/protonation equilibria as well as competing direct C=N or C=O hydrogenation have been excluded.