The thesis concerns with the intermolecular Diels-Alder reactions of masked o-benzoquinones (MOBs) with 6,6-Dimethylfulvene. Masked o-benzoquinones (MOBs) 2a-e generated in situ from 2-methoxyphenols 1a-e underwent intermolecular Diels-Alder reactions with a diene, 6,6-dimethylfulvene to give cycloadducts, tricycle[5.2.2.02,6] undecaenones 3a-e, which were formed from the reactions that MOBs serve as diene and 6,6-dimethylfulvene as a dienophile.