Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Oct 26;57(44):14593-14596.
doi: 10.1002/anie.201808919. Epub 2018 Oct 5.

Enantioselective Lewis Acid Catalyzed ortho Photocycloaddition of Olefins to Phenanthrene-9-carboxaldehydes

Simone Stegbauer  1 , Christian Jandl  1 , Thorsten Bach  1
Affiliations

Enantioselective Lewis Acid Catalyzed ortho Photocycloaddition of Olefins to Phenanthrene-9-carboxaldehydes

Simone Stegbauer et al. Angew Chem Int Ed Engl. .

Abstract

Visible-light irradiation (λ=457 nm) enabled the enantioselective ortho photocycloaddition of olefins to phenanthrene-9-carboxaldehydes (15 examples, 46-93 % yield, 82-98 % ee). A chiral oxazaborolidine Lewis acid (20 mol %) was employed as the catalyst. It operates by coordination to the aldehyde inducing a bathochromic absorption shift beyond the nπ* absorption of the uncomplexed aldehyde. At long wavelengths the Lewis acid complex is exclusively excited; within the complex, one enantiotopic face of the aromatic aldehyde is efficiently shielded. Lewis acid coordination also alters the type selectivity and the simple diastereoselectivity of the photocycloaddition.

Keywords: Lewis acids; arenes; chromophores; cycloaddition; enantioselectivity; photochemistry.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
UV/Vis spectrum of compound 1 a (c=0.25 mm in CH2Cl2) in the presence of variable equiv of EtAlCl2.
Figure 2
Figure 2
Absolute configuration of product 2 c as determined by anomalous X‐ray diffraction and model for the association of Lewis acid 3 c to phenanthrene‐9‐carboxaldehyde 1 c.
Scheme 1
Scheme 1
Lewis acid catalyzed, enantioselective photocycloaddition reactions of phenanthrene‐9‐carboxaldehydes 1 a and 1 d to cyclopentene.
Scheme 2
Scheme 2
Lewis acid catalyzed, enantioselective photocycloaddition of phenanthrene‐9‐carboxaldehyde (1 a) with cyclohexene and isopropylidenecyclohexane to products 6 a and 7.
Figure 3
Figure 3
Structure of photocycloaddition products rac‐8, rac‐4 b, rac‐5 b, rac‐6 b, and rac‐6 c.
See this image and copyright information in PMC

References

    1. None
    1. Silvi M., Melchiorre P., Nature 2018, 554, 41–49; - PubMed
    1. Garrido-Castro A. F., Maestro M. C., Alemán J., Tetrahedron Lett. 2018, 59, 1286–1294;
    1. Ramamurthy V., Sivaguru J., Chem. Rev. 2016, 116, 9914–9993; - PubMed
    1. Brimioulle R., Lenhart D., Maturi M. M., Bach T., Angew. Chem. Int. Ed. 2015, 54, 3872–3890; - PubMed
    2. Angew. Chem. 2015, 127, 3944–3963.

Publication types