Nazarov Synthesis of Cyclopentenones and Some of their Reactions

Abstract

During the creation of a molecular library of cyclopentenones, we discovered a new variant of the allenyl Nazarov cyclization process. The compounds that were being created for the library were β-aminoketones and epoxides that were synthesized using cyclopentenones as the precursor molecule. The precursory cyclopentenones were synthesized using the allenyl Nazarov cyclization variant developed by Dr. Tius. We wished to investigate the reactions that could be performed on these Nazarov adducts to further expand the number of compounds that may be created using the allenyl Nazarov. During the project, a new variant of the allenyl Nazarov process was discovered. The new reaction utilizes a Lewis acid, specifically ytterbium (Ill) triflate to catalyze the electrocyclic ring closure of an allenyl aryl ketone. Literature experiments similar to our reaction have shown re-aromatization of the aryl group that participates in the ring closure. Our new method yields a cyclized product in which aromaticity has been disrupted. Further experimentation and optimization of the methodology is needed, as preliminary reactions have shown poor yields (30%); however this methodology presents exciting new synthesis possibilities.