The crystal structures of a chiral aminoalkoxide cluster and its adduct with benzyllithium

The crystal structures of the chiral aminoalkoxide cluster (S)-2 and its unexpected adduct with benzyllithium (S)-3 have been determined. For compound (S)-2, a hexameric cyclic ring-ladder is observed in the solid state, which leads to an unshielded coordination site in a chiral pocket that is only accessible from one direction. The presence of (S)-2 leads to the deprotonation of toluene by n-butyllithium, giving benzyllithium. In contrast to earlier studies on lithium alkoxides, the resulting adduct (S)-3 between benzyllithium and (S)-2 is not formed by the exchange of alkoxy groups for alkanide units, as has been observed for a multitude of examples. Compound (S)-3 therefore represents a thus far unconsidered type of structure: the unshielded "top side" of the aminoalkoxide cluster (S)-2 capped by the lithium center of benzyllithium via three Li-O interactions.