SYNTHESIS AND PROPERTIES OF A BIS(2-BUTENO)-BRIDGED BIS(ADAMANTANE) -X-RAY AND MOLECULAR DYNAMIC STUDIES OF THE TRANS,TRANS ISOMER

The synthesis of the trans,trans isomer of the bis(2-buteno)-bridged b is(adamantane) 3 has been developed, and its structure was established by spectral and X-ray structure analysis. Since the results of dynami c NMR studies indicate that 3 is conformationally mobile and the trans ition-state free energy (Delta G(c)(not equal)) required to interconve rt two equivalent conformers was estimated to be ca. 60 kJ mol(-1), th e lowest energy conformer was subjected to a molecular dynamic simulat ion 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 C-2h is very close to that found in solution at -50 degrees C, but dif fers from that which was observed in the solid state by X-ray-crystall ographic analysis.