{LiCH(CH2CH2OMen)SO2Ph}4] (OMen = Menthyl): Synthesis and First Structure of a Chiral Solvent Free Lithiated Sulfone with a Direct Li–C Bond

Abstract

AbstractR*OCH2CH2CH2SO2Ph (R*OH = MenOH, (–)‐menthol, (3a); BorOH, (1S)‐(–)‐borneol, (3b)) were found to react with n‐BuLi in n‐pentane/n‐hexane and toluene/n‐hexane under deprotonation yielding LiCH(CH2CH2OR*)SO2Ph (R* = Men, (4a); Bor, (4b)) which reacted with n‐Bu3SnCl forming the requisite tri(n‐butyl)tin compounds n‐Bu3SnCH(CH2CH2OR*)SO2Ph (R* = Men, (5a); Bor, (5b)) as diastereomeric mixtures. The identities of 5a and 5b were unambiguously proved by 1H, 13C and 119Sn NMR spectroscopic measurements. Solutions of 4a afforded crystals of [{LiCH(CH2CH2OMen)SO2Ph}4] (4a′) for which the structure was determined by single‐crystal X‐ray crystallography. Complex 4a′ crystallized in a tetrameric structure without any additional solvent molecules. There were found direct Li–C bonds (Li1–C1/Li2–C20 2.231(9)/2.236(9) Å). The tetrahedral donor set of Li is completed by three oxygen atoms. One oxygen atom comes from the OMen substituent via intramolecular coordination and two oxygen atoms come from SO2 groups of neighboured LiCH(CH2CH2OMen)SO2Ph moieties. Thus, a heterocubane structure with a Li4S4 core is built up.