Characterization of beta-amino ester enolates as hexamers via 6Li NMR spectroscopy.
Low-temperature 6Li NMR spectroscopic studies on a chiral beta-amino ester enolate reveal a complex mixture of homo- and heterochiral aggregates. Subsequent warming of the samples led to rapid intra-aggregate exchange, resulting in four distinct resonances consistent with an ensemble of hexamers. An implicit fit of the aggregate populations to the Boltzmann distribution provided the free energy differences and equilibrium constants. An X-ray crystal structure obtained from the racemic enolate is consistent with the predominant aggregate in solution.
McNeil
Anne J
AJ
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA.
Toombes
Gilman E S
GE
Chandramouli
Sithamalli V
SV
Vanasse
Benoit J
BJ
Ayers
Timothy A
TA
O'Brien
Michael K
MK
Lobkovsky
Emil
E
Gruner
Sol M
SM
Marohn
John A
JA
Collum
David B
DB
D000478:Alkylation; D000605:Amino Alcohols / Q000737:chemistry*; D007202:Indicators and Reagents; D007554:Isotopes; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D013696:Temperature
D000605:Amino Alcohols; D007202:Indicators and Reagents; D007554:Isotopes; D008094:Lithium