Inter- and intramolecular cycloaddition reactions of 2H-chromenes

The research described in this thesis concerns a study of a series of inter- and intramolecular cycloaddition reactions of the carbon-carbon double bond of 2H-chromenes. Firstly, a series of mono-2H-chromenes were prepared and it was shown that numerous intermolecular cycloaddition reactions could be performed. These findings were then applied to a C3-symmetric tris-2H-chromene in order to prepare complex polycyclic compounds in a highly efficient manner. For example, a cycloaddition reaction product was prepared in two steps from readily-available starting materials that contained seven fused rings and six stereogenic centres. Moreover, the regiochemistry and stereoselectivities of these cycloaddition processes were determined. A series of intramolecular cycloaddition reactions were then attempted on mono- and tris-2H-chromenes. It was found that intramolecular [2+2] cycloadditions proceeded adequately, however, intramolecular [2+4] cycloadditions were unsuccessful. Thus, preliminary investigations were then undertaken towards the synthesis of functionalized 2H-chromenes that would contain a more reactive carbon-carbon double bond.