Transition structure geometries for transfers of neutral and anionic nitrogen to lithiated carbanions

Citation
P. Beak et al., Transition structure geometries for transfers of neutral and anionic nitrogen to lithiated carbanions, J ORG CHEM, 64(14), 1999, pp. 5218-5223
Citations number
59
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
JOURNAL OF ORGANIC CHEMISTRY
ISSN journal
0022-3263 → ACNP
Volume
64
Issue
14
Year of publication
1999
Pages
5218 - 5223
Database
ISI
SICI code
0022-3263(19990709)64:14<5218:TSGFTO>2.0.ZU;2-H
Abstract
The geometries of nucleophilic substitutions at neutral and. anionic nitrog en by organolithium species have been investigated. The demonstration of an intramolecular conversion of 9 to 10 provides an endocyclic restriction te st which supports a trigonal bipyramidal transition structure for nitrogen transfer. A lack of isotopic scrambling of 12a-O-18 during nitrogen transfe r is taken to rule out reaction via an orient-ed ion pair. Attempted endocy clic restriction tests for transfers of formally anionic nitrogen with 32 a nd 33 were not successful. Reactions of n-butyl, s-butyl and tert-butyllith ium 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 rea gent. These results are consistent with trigonal bipyramidal transition sla tes for nucleophilic displacements of oxygen by carbon at neutral and anion ic nitrogen.