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Sequential aminodiene Diels-Alder approach to the ergoline skeleton
Albert Padwa1, Scott K Bur, Hongjun Zhang
1Department of Chemistry, Emory University, Atlanta, GA 30322, USA. chemap@emory.edu
The Journal of Organic Chemistry
|August 13, 2005
Summary
This study details a novel aminodiene Diels-Alder reaction sequence for synthesizing tricyclic ketones. While the route to lysergic acid was ultimately unsuccessful due to regioselectivity issues, it showcases valuable synthetic strategies.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- Diels-Alder reactions are crucial for forming cyclic compounds.
- Amidofurans and cyclohexenones are versatile building blocks in organic synthesis.
Purpose of the Study:
- To develop a novel sequence of aminodiene Diels-Alder reactions for synthesizing substituted amidofurans.
- To explore the conversion of these amidofurans into tricyclic ketones.
- To investigate an expeditious route towards lysergic acid.
Main Methods:
- Intramolecular Diels-Alder cycloaddition of amidofurans with tethered cyclohexenones.
- Utilizing Rawal's aminodiene chemistry for cyclohexenone construction.
- Transformation of a Kornfeld ketone analogue to a vinyl triflate for palladium-catalyzed cross-coupling.
Main Results:
- Several substituted amidofurans were efficiently converted to tricyclic ketones via a novel reaction sequence.
- An angular carbomethoxy group was found to activate the olefin and prevent isomerization.
- The synthesis of lysergic acid was attempted but could not be completed due to regioselectivity challenges in a Heck reaction.
Conclusions:
- The developed methodology provides a facile route to tricyclic ketones.
- The study highlights the utility of aminodiene chemistry and Diels-Alder reactions in complex molecule synthesis.
- Further optimization is needed to overcome regioselectivity issues for the successful synthesis of lysergic acid.