Electronic Influences on the Dynamic Range of Photoswitchable Dithienylethene-Thiourea Organocatalysts
Debashis Majee1, Gabriele Ramanauskaite1, Stanislav Presolski1
1Division of Science, Yale-NUS College, Singapore 138527, Singapore.
Abstract:
Thiourea-based organocatalysts bearing a photoswitchable dithienylethene (DTE) core and a wide range of substituents were prepared and extensively tested for their ability to accelerate the Michael reaction between acetylacetone and trans-β-nitrostyrene. There is a strong correlation between the Hammett parameter of the modulating groups and catalytic activity following UV irradiation. Electron-withdrawing groups afford the largest reactivity difference between the catalysts in their ring-open form and their ring-closed isomer, with evidence for electronic coupling between the two halves in both oDTE and cDTE.
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