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Intermolecular and intramolecular energy flow and subsequent bond dissociation in collinear collisions I–C≡C–H+Ar and I–C≡C–C≡C–H+Ar have been studied by classical trajectory techniques over the collision energy range of 0 to 10 eV. When the molecule is initially in the ground state, the overall energy transfer in I–C≡C–H+Ar is very small, but in I–C≡C–C≡C–H+Ar it is large. The collisionally perturbed C–H bond stores a large amount of energy from translation for a brief period during the early stage of collision and transfers most of it to the inner region of the molecule, specifically to the low frequency C–I vibration. Thus the high‐frequency vibration of the perturbed C–H bond during the collision plays a crucial role in determining the extent of intramolecular energy transfer and, in turn, C–I dissociation. But in nondissociative collisions, there is another series of the C–H vibration at the latter stage of collision, transferring energy back to translation. This study also considers collision‐induced intramolecular energy flow in the molecule with an initially excited C–H bond. The relaxation of the low‐lying C–H excitation is very slow on a nanosecond time scale. However, when the excitation is high, the vibrational frequency of the C–H bond is significantly weakened, thus becoming comparable to that of the triple bond, in which case the isolating effect of the adjacent C≡C bond is no longer important and intramolecular energy flow becomes efficient.

Chiral phosphinoimidazolidine 3 was used as an excellent ligand in Pd-catalyzed asymmetric allylic alkylation of racemic 1,3-diphenyl-2-propenyl acetate 5 with dimethyl malonate. Outstanding enantioselectivity of up to 99% and remarkable catalytic activity were observed. The ligand was also found to be effective in the asymmetric allylic amination of 5 with benzylamine.

Optically active amino thiocyanate derivatives of (−)-norephedrine were found to act as effective aprotic ligands for enantioselective addition of diethylzinc to aldehydes. This reaction provided optically active secondary alcohols with ee up to 96%.

School of Chemical Science & Engineering, Inha University, Inchon 402-751, KoreaReceived February 23, 2004Key Words : Enantioselective addition, Polymer-supported ligand, Amino thioacetate, DiethylzincEnantioselective addition of dialkylzinc to aldehydes inthe presence of a catalytic amount of chiral ligands is knownto be one of the most important methods for the synthesis ofoptically active secondary alcohols.