Background:
Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate
capable of undergoing multiple types of transformations due to three key structural features:
a free alkene, a bridged oxygen atom, and a highly strained ring system. Most notably,
ring-opening reactions of OBD using transition metal catalysts and nucleophiles produce
multiple stereocenters in a single step. The resulting dihydronaphthalene framework
is found in many natural products, which have been shown to be biologically active.
Objective:
This review will provide an overview of transition metal-catalyzed reactions
from the past couple of years including cobalt, copper, iridium, nickel, palladium and rhodium-
catalyzed reactions. In addition, the recent derivatization of OBD to
cyclopropanated oxabenzonorbornadiene and its reactivity will be discussed.
Conclusion:
It can be seen from the review, that the work done on this topic has employed the use of many different
transition metal catalysts, with many different nucleophiles, to perform various transformations on the
OBD molecule. Additionally, depending on the catalyst and ligand used, the stereo and regioselectivity of the
product can be controlled, with proposed mechanisms to support the understanding of such reactions. The use
of palladium has also generated a cyclopropanated OBD, with reactivity similar to that of OBD. An additional
reactive site exists at the distal cyclopropane carbon, giving rise to three types of ring-opened products.
Silicon Grignard Reagents as Nucleophiles in Transition-Metal-Catalyzed Allylic Substitution
