:
Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate which can be readily activated by transition
metal complexes with great face selectivity due to its dual-faced nature and intrinsic angle strain on the alkene. To date, the
understanding of transition-metal catalyzed reactions of OBD itself has burgeoned; however, this has not been the case for
unsymmetrical OBDs. Throughout the development of these reactions, the nature of C1-substituent has proven to have a
profound effect on both the reactivity and selectivity of the outcome of the reaction. Upon substitution, different modes of
reactivity arise, contributing to the possibility of multiple stereo-, regio-, and in extreme cases, constitutional isomers which
can provide unique means of constructing a variety of synthetically useful cyclic frameworks. To maximize selectivity, an
understanding of bridgehead substituent effects is crucial. To that end, this review outlines hitherto reported examples of
bridgehead substituent effects on the chemistry of unsymmetrical C1-substituted OBDs.
