Synthesis and Properties of a Bis(2-buteno)-Bridged Bis(adamantane): X-ray and Molecular Dynamic Studies of thetrans, trans Isomer

Abstract

The synthesis of the trans,trans isomer of the bis(2-buteno)-bridged bis(adamantane) 3 has been developed, and its structure was established by spectral and X-ray structure analysis. Since the results of dynamic NMR studies indicate that 3 is conformationally mobile and the transition-state free energy (ΔGc≠) required to interconvert two equivalent con-formers was estimated to be ca. 60 kJ mol−1, the lowest energy conformer was subjected to a molecular dynamic simulation at 323 K in the gas phase. Three conformations 3a, 3b and 3c were found. The conformations 3a and 3c have anti-oriented adamantane units, while in 3b the adamantane molecules occupy the syn conformation. By analysing the conformational processes in macrocyclic diene 3, it was found that the calculated conformation 3a with molecular symmetry of C2h is very close to that found in solution at –50 °C, but differs from that which was observed in the solid state by X-ray-crystallographic analysis.