Organic Chemistry

Photochemical Synthesis of (2E,4Z)-5-(anthracen-9-yl)-2-cyanopenta-2,4-dienamide



In this short note we describe the photochemical synthesis of (2E,4Z)-5-(anthracen-9-yl)-2-cyanopenta-2,4-dienamide (4) from the corresponding (2E,4E)-5-(anthracen-9-yl)-2-cyanopenta-2,4-dienamide (3) and subsequent purification by precipitation from aqueous surfactant. Compound like 4 belongs to a family of anthracene derivatives capable of forming crystals that can photo-mechanically deform with light. Synthesis of 3 was achieved with high yields and in less than one minute via secondary amine-catalyzed Knoevenagel condensation between commercially available (E)-3-(anthracen-9-yl)acrylaldehyde (1) and 2-cyanoacetamide (2). Photochemical conversion of a solution of the 3 in acetonitrile using light > 475 nm from a commercial blue LED leads to a mixture of 4 (87%) and unconverted 3 (13%) due to the presence of a photostationary state from overlapping absorption spectral regions. Pure 4 ( >99%) was later obtained by precipitating an organic sol1ution of the photoproduct from aqueous surfactant Sodium Dodecyl Sulfate (SDS). Pure 4 was collected in the form of acicular micro crystals that are photomechanically responsive to UV light. The products were analyzed using 1H NMR, 13C NMR, IR, UV-Vis, and HPLC.


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