Asymmetric Roadmap to Diverse Polycyclic Benzopyrans via Phosphine-Catalyzed Enantioselective [4 + 2]-Annulation
Adithi Danda1,2, Naredla Kesava-Reddy1, Christopher Golz2
1Max-Planck-Institut für Molekulare Physiologie , Abteilung Chemische Biologie, Otto-Hahn-Straße 11, 44227 Dortmund, Germany.
Abstract:
The catalytic addition of the amino acid derived bifunctional N-acylaminophosphine to an α-substituted allene ester generated a zwitterionic dipole that engaged the vinylogous ester function of 3-cyano-chromones in a [4 + 2] annulation reaction to deliver tetrahydroxanthones embodying three consecutive chiral centers in high yields and with excellent enantioselectivities. The established asymmetric synthesis further paves the way to two different classes of complex, sp(3)-rich tetracyclic benzopyrans via efficient cascade reactions.
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