Abstract
The first chapter describes TpRu(PPh3)(CH3CN)2PF6 catalyzed cyclization of epoxide-alkyne. The reaction products are highly dependent on the substituent and structural skeleton of the epoxide substrates. We propose a plausible mechanism involving ketene-alkene intermediates, generated from an oxygen migration from epoxide to terminal alkyne. This proposed mechanism is supported by trapping experiments using isobutyl alcohol as well as deuterium labeling experiment. Examination of this reaction on molecules bearing various alkyne-epoxide functionalities is under investigation. The second chapter discusses TpRu(PPh3)(CH3CN) 2PF6 catalyzed cyclization of 1-(2’-iodoethynylphenyl)- 2-alkyloxiranes gave 1-iodonaphthan-2-ol derivatives in DMF very efficiently, but preferably yielded 6-iodo-7-oxa-benzocycloheptene in benzene. The active intermediates in DMF and benzene were ruthenium-2-iodovinylidene and π-iodoalkyne species respectively. The intramolecular attack of epoxide at the π-iodoalkyne intermediate preferably proceeds via a 7-endo-dig cyclization, and this unusual pathway is attributed to the electronic effect of an iodo substituent. The third chapter describes PtCl2 catalyzed cycloisomerization of cis-4,6-dien-1-yn-3-ols with an unusual skeletal rearrangement; this catalytic reaction is applicable to a wide range of substrates. Its 1,3-alkylidene migration pathway is clearly established by isotope-labeled experimental evidences. Application of this new catalysis of complex molecule is under current investigation. The fourth chapter describes PtCl2/CO catalyzed cycloisomerization of (cyclopent-1-enyl)prop-2-yn-1-ol to cyclopropane derivatives. This catalytic reaction is applicable to substrates that contain heteratom compounds. Further application of our synthetic method for the synthesis of naturally occurring compounds is under current investigation. The last chapter describes AuCl catalyzed cycloisomerization of alkene and electron-withdrawing alkyne. These new gold-catalyzed reaction is applicable to ketone and ester substituents. Its mechanism is clearly established by isotope-labeled experimental evidences. Application of this new catalysis of complex molecule is under current investigation.