Abstract
s‐Block metal carbenoids are carbene synthons and applied in a myriad of organic transformations. They exhibit a strong structure–activity relationship, but this is only poorly understood due to the challenging high reactivity and sensitivity of these reagents. Here, we report on systematic VT and DOSY NMR studies, XRD analyses as well as DFT calculations on a sulfoximinoyl‐substituted model system to explain the pronounced solvent dependency of the carbenoid stability. While the sodium and potassium chloride carbenoids showed high stabilities independent of the solvent, the lithium carbenoid was stable at room temperature in THF but decomposed at −10 °C in toluene. These divergent stabilities could be explained by the different structures formed in solution. In contrast to simple organolithium reagents, the monomeric THF‐solvate was found to be more stable than the dimer in toluene, since the latter more readily forms direct Li/Cl interactions which facilitate decomposition via α‐elimination.
Highlights
Polar organometallics, organolithium or Grignard reagents are amongst the most important organometallic compounds used in synthetic chemistry
Based on sulfoximinoyl-substituted alkali metal carbenoids we could show using a combination of VT-DOSY NMR experiments together with X-ray diffraction analysis (XRD) analyses and computational studies that the carbenoids form monomers in coordinating solvents (THF), while they aggregate to dimers in toluene
The sulfoximinoyl moiety was selected due to three reasons: i) sulfoximine carbenoids have successfully been employed in carbenoid chemistry such as for asymmetric cyclopropanations and are of synthetic interest.[ 13 ] ii) The sulfoximinoyl group together with the thiophosphoryl unit promised sufficient stabilization of the carbenoid to allow a controlled handling. iii) The stereocentre at sulfur offered a further spectroscopic probe which might provide further information about the structure formation in solution
Summary
Katharina Dilchert[a,b], Michelle Schmidt[a], Angela Großjohann[a], Kai-Stephan Feichtner[a], Robert E. Abstract: s-Block metal carbenoids are carbene synthons and applied in a myriad of organic transformations. They exhibit a strong structure-activity relationship, but this is only poorly understood due to the challenging high reactivity and sensitivity of these reagents. While the sodium and potassium chloride carbenoids showed high stabilities independent of the solvent, the lithium carbenoid was stable at room temperature in THF but decomposed at −10 °C in toluene. These divergent stabilities could be explained by the different structures formed in solution. In contrast to simple organolithium reagents, the monomeric THFsolvate was found to be more stable than the dimer in toluene, since the latter more readily forms direct Li/Cl interactions which facilitate decomposition via α-elimination
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