TY - JOUR
T1 - Tricyclic Sulfoxide–Alkene Hybrid Ligands for Chiral Rh(I) Complexes: The “Matched” Diastereomer Catalyzes Asymmetric C–C Bond Formations
AU - Nikol, Alexander
AU - Zhang, Ziyun
AU - Chelouan, Ahmed
AU - Falivene, Laura
AU - Cavallo, Luigi
AU - Herrera, Alberto
AU - Heinemann, Frank W.
AU - Escalona, Ana
AU - Frieß, Sibylle
AU - Grasruck, Alexander
AU - Dorta, Romano
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank Prof. Anthony Linden (University of Zurich) for solving the crystal structure of 8 and Ms. Christina Wronna for carrying out the elemental analyses. Financial support by Friedrich–Alexander University and King Abdullah University of Science and Technology (KAUST) is acknowledged. For computer time, this research used the resources of the Supercomputing Laboratory (KSL) at KAUST.
PY - 2020/3/19
Y1 - 2020/3/19
N2 - Deprotonation of phenyldibenzo[b,f]tropylidene (8) with LDA/t-BuOK followed by quenching with either diastereomer of inexpensive
glucose-based t-Bu-sulfinate (R)- or (S)-11 affords a sulfoxide−alkene hybrid ligand as the diastereomeric pairs (SS,SC)-9/(SS,RC)-10 and (RS,RC)-9/ (RS,SC)-10, respectively, which via chromatographic/recrystallization may be separated into the four isomers. The optically pure diastereomeric ligands (SS,SC)-9 and (SS,RC)-10 react with [RhCl(coe)2]2 to form the dinuclear complexes (RS,SC)-11 and (RS,RC)-12, respectively, in which the bidentate ligands coordinate the metal centers through the sulfur and alkene donor functions. These complexes catalyze the conjugate addition of arylboronic acids to cyclic Michael acceptors with enantioselectivities of up to 99% ee. DFT calculations show the preponderant influence of planar chirality of the ligand alkene function. The enantioselectivity switch observed between (RS,SC)-11 and (RS,RC)-12 is explained by the inverted cis−trans coordinations of the substrate molecules in catalytic steps.
AB - Deprotonation of phenyldibenzo[b,f]tropylidene (8) with LDA/t-BuOK followed by quenching with either diastereomer of inexpensive
glucose-based t-Bu-sulfinate (R)- or (S)-11 affords a sulfoxide−alkene hybrid ligand as the diastereomeric pairs (SS,SC)-9/(SS,RC)-10 and (RS,RC)-9/ (RS,SC)-10, respectively, which via chromatographic/recrystallization may be separated into the four isomers. The optically pure diastereomeric ligands (SS,SC)-9 and (SS,RC)-10 react with [RhCl(coe)2]2 to form the dinuclear complexes (RS,SC)-11 and (RS,RC)-12, respectively, in which the bidentate ligands coordinate the metal centers through the sulfur and alkene donor functions. These complexes catalyze the conjugate addition of arylboronic acids to cyclic Michael acceptors with enantioselectivities of up to 99% ee. DFT calculations show the preponderant influence of planar chirality of the ligand alkene function. The enantioselectivity switch observed between (RS,SC)-11 and (RS,RC)-12 is explained by the inverted cis−trans coordinations of the substrate molecules in catalytic steps.
UR - http://hdl.handle.net/10754/662258
UR - https://pubs.acs.org/doi/10.1021/acs.organomet.0c00094
UR - http://www.scopus.com/inward/record.url?scp=85082312662&partnerID=8YFLogxK
U2 - 10.1021/acs.organomet.0c00094
DO - 10.1021/acs.organomet.0c00094
M3 - Article
JO - Organometallics
JF - Organometallics
SN - 0276-7333
ER -