CHIRAL HOMOENOLATE EQUIVALENTS .4. CRYSTAL-STRUCTURE OF A CHIRAL 1-AMINOALLYLLITHIUM COMPOUND - DIMERIC, INTRAMOLECULARLY CHELATED (3S)-3-LITHIO-1-[(S)-2-(METHOXYMETHYL)PYRROLIDINO]-1,3-DIPHENYLPROPENE

Chiral Homoenolate Equivalents, IV. — Crystal Structure of a Chiral 1‐Aminoallyllithium Compound: Dimeric, Intra‐molecularly Chelated (3S)‐3‐Lithio‐1‐[(S)‐2‐(methoxymethyl)pyrrolidino]‐1,3‐diphenylpropene The chiral title compound crystallizes from toluene as a dimer. Two molecules toluene cocrystallize outside the aggregate. The 1‐aminoallyl group is nearly planar. Both exo‐placed phenyl groups and the endo‐placed pyrrolidine group are twisted against the allylic plane. The nitrogen atom is pyramidal, the lone pair is directed to the allyl group (in‐conformer). The bond angle C1‐C2‐C3 is widened, and the bond distances C1‐C2 and C2‐C3 alternate slightly. This is indicative of a strongly delocalized 3‐metallated enamine structure. The lithium atom of one monomer unit is bound to the C3 atom and chelated intramolecularly by the nitrogen and oxygen atoms. Therefore it is placed on the Si side of the allylic plane. Its free coordination site is occupied by the benzyl group of the second monomer unit. The dimer can hence be regarded as being an allyl‐ as well as a benzyllithium compound at the same time. MNDO calculations reproduce the results of the X‐ray structure determination satisfactorily and allow some insight into possible structures in solution. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim