The geometries of nucleophilic substitutions at neutral and anionic nitrogen by organolithium species
have been investigated. The demonstration of an intramolecular conversion of 9 to 10 provides an
endocyclic restriction test which supports a trigonal bipyramidal transition structure for nitrogen
transfer. A lack of isotopic scrambling of 12a-18
O during nitrogen transfer is taken to rule out
reaction via an oriented ion pair. Attempted endocyclic restriction tests for transfers of formally
anionic nitrogen with 32 and 33 were not successful. Reactions of n-butyl, s-butyl and tert-butyllithium reagents with 16, 23, 30, 31, and 36−38 generally afford higher yields with increasing
substitution at the carbon of the organolithium reagent and with decreasing substitution adjacent
to the nitrogen of the aminating reagent. These results are consistent with trigonal bipyramidal
transition states for nucleophilic displacements of oxygen by carbon at neutral and anionic nitrogen.
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