Abstract
Quinone methides (quinomethanes) act as important intermediates
in organic syntheses, as well as in chemical and biological processes.
However, examples of such isolated species are scarce owing to their
high reactivity. Other important reactive intermediates are thio-
and selenoquinones. However, unlike quinones, they are highly unstable
and consequently do not exist in nature, hence their chemical and
biological properties remain unknown. In this account, we describe
the first isolation of the above important reactive intermediates,
by π-coordination to a (pentamethylcyclopentadienyl)iridium
(Cp*Ir) moiety, and their X-ray molecular structures. Further,
the reactivity of such trapped intermediates is reported. For instance,
the metalated o -quinone methide underwent an
unusual cycloaddition reaction compared with the free o -quinone methide, while the metalated
thioquinones were successfully used as organometallic linkers (OM-linkers)
to construct luminescent coordination assemblies. The anticancer
activity of the selenoquinone metalated complex was studied, together
with related oxygen and sulfur analogues, and remarkably it was
shown to be the only cytotoxic compound with a comparable activity
to cisplatin.
1 Introduction
2 Quinone Methides
2.1 First Isolation of Metal-Stabilized o -Quinone
Methides
2.1.1 Synthesis and Structural Characterization
2.1.2 Reactivity towards Electrophiles and Carbon-Carbon
Bond Formation
3 Thioquinones
3.1 First Isolation as Metal Complexes
3.1.1 Synthesis and Structural Characterization
3.1.2 Reactivity as Organometallic Linkers
4 Selenoquinones
4.1 Trapping Selenoquinones as Metal Complexes
4.1.1 Synthesis and Structural Characterization
4.1.2 Biological Properties
5 Concluding Remarks and Future Outlook
Key words
reactive intermediates - iridium - metal-stabilized o -quin-one methides - metal-stabilized
thioquinones - metal-stabilized selenoquinones - anticancer
activity