Modern Variants
The shortcomings noted above limit the usefulness of the Nazarov cyclization reaction in its canonical form. However, modifications to the reaction focused on remedying its issues continue to be an active area of academic research. In particular, the research has focused on a few key areas: rendering the reaction catalytic in the promoter, effecting the reaction with more mild promoters to improve functional group tolerance, directing the regioselectivity of the elimination step, and improving the overall stereoselectivity. These have been successful to varying degrees.
Additionally, modifications focused on altering the progress of the reaction, either by generating the pentadienyl cation in an unorthodox fashion or by having the oxyallyl cation "intercepted" in various ways. Furthermore, enantioselective variants of various kinds have been developed. The sheer volume of literature on the subject prevents a comprehensive examination of this field; key examples are given below.
Read more about this topic: Nazarov Cyclization Reaction
Famous quotes containing the words modern and/or variants:
“The medieval university looked backwards; it professed to be a storehouse of old knowledge.... The modern university looks forward, and is a factory of new knowledge.”
—Thomas Henry Huxley (1825–1895)
“Nationalist pride, like other variants of pride, can be a substitute for self-respect.”
—Eric Hoffer (1902–1983)