Danda, A., Naredla, K. R., Golz, C., Strohmann, C., & Kumar, K. (2016). Asymmetric Roadmap to Diverse Polycyclic Benzopyrans via Phosphine-Catalyzed Enantioselective [4 + 2]-Annulation Reaction. Organic Letters, 18(11), 2632-2635. doi:10.1021/acs.orglett.6b01030.