Ladder-type tetramers

The lithium derivative of the chiral chelating diamine (3 )-2-(l-pyrrolidinylmethyl)-pyrrolidine (6) has been used extensively in stereoselective synthesis, i.e. in the deprotonation of ketones and rearrangement of epoxides to homoallylic alcohols. The lithium amide has been crystallized from toluene solution, and X-ray analysis revealed that it forms a ladder-type tetramer with the two pyrrolidine nitrogens solvating the two lithiums at the end of the ladder38, (Li-6)4. 

Lithium amide 4 has been crystallized from toluene and X-ray crystallography has shown that the crystals are made up of tetramers of ladder type (4g) (Scheme 6) [31]. 

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