Abstract
Intramolecular cyclization of enynes mediated by organocobalt and ruthenium are discussed in this thesis. In the first chapter, we prepared a series of chiral 3,4-bisallyoxy-but-1-ynes having syn and anti configurations. Treatment of these substrates with Grubbs catalyst CL2(PCy3)2Ru=CHPh preferably gave chiral dioxabicyclo[4.4.0]- decane in addition to dioxabicyclo[5.3.0]decane in minor properties. On substitution of the 4-but-2-enyloxy group, the metathesis reactions produced only dioxabicyclo[5.3.0]decane in the presence of Grubbs ruthenium-imidazolidene carbine catalyst. The second chapter discusses Co2(CO)8-mediated coupling of cis-epoxyalkyne, CO, and olefin functionalities, leading to tandem [5+1]/[2+2+1] and [5+1]/[2+2]-cycloaddition reactions to give tricyclic δ–lactones efficiently. The mechanism involves cyclocarbonylation to form δ–lactone intermediate, followed by oxidative cyclization to give cobalt-containing cyclopentane species. Insertion of CO or reductive elimination of this species leads to the derivative of cyclopentanone or cyclobutane products, respectively. The third chapter describes TpRu(PPh3)(CH3CN) 2PF6 catalyzed aromatization of unfunctionalized endiynes. In the case of endiynes bearing a long alkyl substituent, the aromatization accompanied by a C-H bond insertion to form a cyclopentane ring. Highly nucleophilic addition of water, alcohols, aniline, acetylacetone, pyrroles and dimethyl malonate to endiynes gave functionalized benzene products in good yields. This method is very useful because it provides easy access to functionalized aromatic compounds from readily available unfunctionalized enediynes.