title: Chiral aldehydes in hydrocarbons: diastereoselective nucleophilic addition, NMR, and CD spectroscopy reveal dynamic solvation effects.
abstract: Temperature-dependent studies on the diastereoselective nucleophilic addition of n- BuLi to alpha-chiral aldehydes as (S)-O-(t-butyl-dimethylsilyl)lactal, (S)-O-(t-butyl-dimethylsilyl) mandelic aldehyde, and (R)-2-phenylpropanal in n-decane and n-dodecane reveal dynamic solvation phenomena with the presence of inversion temperatures (T(inv)) in the Eyring plots of ln (anti/syn) vs. 1/ T. These dynamic solvent effects were disclosed by temperature-dependent studies of the (13)C NMR, CD, and UV spectra of the starting aldehydes in solution of n-decane and n-dodecane. The concomitant presence of three peculiar temperatures T(CD), T(UV), and T(NMR), whose values are identical and match T(inv), clearly confirms our earlier interpretation of the solvent-dependent nature of T(inv). The inversion temperature, as well as T(CD), T(UV), and T(NMR) represents the interconversion temperature of two different solvation clusters which act as two different supramolecules with different stereoselectivities.
authors: Dipartimento di Chimica G. Ciamician, Alma Mater Studiorum--Università di Bologna, Bologna, Italy. giacomin@ciam.unibo.it
authors: Gianfranco
authors: G
authors: Cainelli
authors: Paola
authors: P
authors: Galletti
authors: Silvia
authors: S
authors: Pieraccini
authors: Arianna
authors: A
authors: Quintavalla
authors: Daria
authors: D
authors: Giacomini
authors: Gian
authors: G
authors: Piero Spada