Functionalization of furfural can be achieved by photocatalytic C−H activation of the aldehyde and coupling to electron-deficient olefins. With (Bu₄N)₄W₁₀O₃₂ as the photocatalyst, furfural can be added to benzylidene malononitriles, acrylates, itaconic anhydride, maleic anhydride, 2-vinylpyridine and phenyl vinyl sulfone to form the corresponding furanyl ketones in moderate-to-good yields.

Abstract

Furfural is produced on a large commercial scale from lignocellulose and can be used for the preparation of several industrial chemicals with four to five carbon atoms. Further functionalization of furfural by C−H activation, however, is less widely developed. In the present work, tetrabutylammonium decatungstate is investigated as an inexpensive photocatalyst for activating the aldehyde C−H bond and mediate a coupling between furfural and electron-deficient olefins. The results show that furfural can be successfully added to benzylidene malononitriles, acrylates, itaconic anhydride, maleic anhydride, 2-vinylpyridine and phenyl vinyl sulfone to generate the corresponding furanyl ketones in moderate-to-good yields. The electronic properties of the electron-deficient olefins are instrumental for achieving a favorable reaction with furfural. The findings show how photocatalysis can be used to form new carbon-carbon bonds from a platform molecule, which in this way can be converted into a number of more advanced structures.