Origins of stereoselectivity in asymmetric syntheses using chiral oxazolines Academic Article uri icon

abstract

  • The structures of chiral oxazoline lithio anions enriched in 13C have been studied by 13C NMR spectroscopy. No rotation about the carbon-carbon bond in the lithio azaallyl anion (5) from (4S,5S)-2-(1-methylethyl)-4-methoxymethyl-5-phenyl-2-oxazoline was observed in 2 h at -50 °C. The ratio of the E (2) and Z (3) isomers formed by deprotonation of (4S,5S)-2-ethyl-4-methoxymethyl-5-phenyl-2-oxazoline varied as a function of the base used for deprotonation (base-solvent, 2:3; lithium diisopropylamide-tetrahydrofuran, 96:4; lithium diisopropylamide-dimethoxyethane, 96:4; n-butyllithium-tetrahydrofuran, 69:31; lithium diisopropylamide-hexamethylphosphoric triamide-tetrahydrofuran, 67:33; lithium diphenylamide-tetrahydrofuran, 80:20). Asymmetric syntheses employing chiral oxazoline lithio anions are discussed in terms of the stereoselectivity of the deprotonation reaction as well as that of the alkylation reaction. © 1978, American Chemical Society. All rights reserved.

author list (cited authors)

  • Hoobler, M. A., Bergbreiter, D. E., & Newcomb, M

complete list of authors

  • Hoobler, MA||Bergbreiter, David E||Newcomb, Martin

publication date

  • January 1, 1978 11:11 AM