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

ABSTRACT: Visible-light irradiation (?=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 n?* 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.

SUBMITTER: Stegbauer S

PROVIDER: S-EPMC6220838 | biostudies-other | 2018 Oct

REPOSITORIES: biostudies-other

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

Stegbauer Simone S Jandl Christian C Bach Thorsten T

Angewandte Chemie (International ed. in English) 20181005 44

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 f ...[more]

PMID: 30225921

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