Chiral aldehydes in hydrocarbons: diastereoselective nucleophilic addition, NMR, and CD spectroscopy reveal dynamic solvation effects

Temperature‐dependent studies on the diastereoselective nucleophilic addition of n‐ BuLi to α‐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. Chirality 16:50–56, 2004. © 2003 Wiley‐Liss, Inc.