Structural studies of {6Li} 2-lithiopyrrolidines using NMR spectroscopy

A selection of N-substituted 2-lithiopyrrolidines were prepared and their structures were investigated by 6Li and 13C NMR spectroscopy. Evidence is presented for aggregation and dynamic solvation effects, depending on the nature of the N-substituent and substituents on the pyrrolidine ring. Studies were performed with N-Boc (coordinating carbonyl group), N-methoxyethyl (coordinating methoxy group) and N-alkyl (no coordinating group) heterocycles to represent three different classes of organolithiums: dipole-stabilized, unstabilized and chelated, and unstabilized.