Catalytic Enantioselective [6π] Photocyclization Reactions by Chromophore Activation with a Chiral Lewis Acid.

ABSTRACT: The [6π] photocyclization of 3-[(1,1'-biphenyl)-2-yl]-2-methylcyclopent-2-enones was found to proceed enantioselectively, when a chiral AlBr₃-activated oxazaborolidine was employed as photocatalyst. A low Lewis acid catalyst loading (2.5-5.0 mol %) was sufficient to induce a high enantioselectivity in the photochemical reaction. A total number of 21 tetracyclic products were obtained as single diastereoisomers in 78-99% ee upon variation of the terminal phenyl ring in the substrate (39-83% yield). Evidence was collected that the chiral Lewis acid coordinates to the enone and induces a bathochromic shift, which allows for selective excitation of the substrate-catalyst complex at λ = 368 nm or λ = 405 nm. The substrate binds to the Lewis acid by coordination of its carbonyl

SUBMITTER: Grunwald D 

PROVIDER: S-EPMC12715800 | biostudies-literature | 2025 Dec

REPOSITORIES: biostudies-literature