UC San Diego

This work mainly focused on exploring mechanism of ruthenium triggered 6π electrocyclization of trienes. The first assignment is the synthesis of trienes, the thermal and photolysis reactions of the all protio terminal triene were carried out in order to compare the efficiency and effectiveness of the traditional cyclization process and the ruthenium mediated reaction. Based on all the results from the all-protio triene reactions, the η4 and η6 intermediates were discovered. Meanwhile, whether the ruthenium accelerated cyclization undergoes a disrotatory proceed is hard to judge. Therefore, deuterium labeled trienes were desired. Deuterium enriched trienes need to be employed as the substrates to clarify the stereochemistry. With the consistency of mechanism proposed by Stryker and the results obtained from the deuterium labelling studies, the ruthenium-mediated disrotatory cyclization process of trienes was demonstrated. Then the kinetic isotopic effect study was achieved, the competition reaction between all-protio triene and triene-d2 demonstrated no isotopic effect appeared in this case, which indicated the rate determine step of the whole cyclization process is not the metal binding step. Lastly, the kinetic studies of terminal triene and three dimethyl triene synthesized by Li-An Wang were carried out to clarified the reacting rate of all these triene and to learn more about the mechanism occurred during the cyclization process.