Photocatalytic Radical Addition to Levoglucosenone

Abstract

Using photocatalysis with tetra‐n‐butylammonium decatungstate (TBADT), alkanes, cyclic acetals, cyclic ethers, formamide and aldehydes were added in a stereoselective way to levoglucosenone (LGO). A hydrogen atom is transferred from the donor compound to the photochemically excited TBADT, and the resulting radicals add onto LGO in a stereoselective way. In the case of the addition of adamantane, two regio‐isomers were obtained which form a crystalline solid solution. Cyrene™, obtained by hydrogenation of LGO, was added under the same conditions. In this case, only two of 32 possible isomers of the resulting Cyrene™ dimer were formed. The regio‐selectivity of the HAT step is discussed in detail. For this purpose, bond dissociation energies and partial charges have been calculated. Transition state calculations of the radical addition to LGO explain the stereospecificity of this reaction step.

Tetrabutylammonium decatungstate (TBADT), a compelling and trailblazing catalyst for visible-light-induced organic photocatalysis

“…TBADT was used as a photocatalyst in a stereoselective photocatalytic radical addition to levoglucosenone, as reported by Hoffmann and coworkers, (Scheme 27). 51 A wide range of radicals derived from alkanes, aldehydes, formamide, cyclic ethers, or cyclic acetals were produced and stereoselectively added to levoglucosenone. TBADT acts as a photocatalyst and an efficient hydrogen abstracting agent in the process.…”

Photocatalytic Transformation of Biomass and Biomass Derived Compounds—Application to Organic Synthesis

“…Photocatalytic reactions have also been performed with this compound. Using tetra-n-butylammonium decatungstate (TBADT) as a photocatalyst, various radical species have been added to levoglucosenone 64 ( Scheme 14 ) [ 188 ]. Thus, alkanes ( 65a ) or cyclic ethers ( 65b ) have been added.…”

Decatungstate‐Catalyzed Carbon‐Carbon Bond Formation Between Furfural and Electron‐Deficient Olefins

“…TBADT has previously been employed for catalyzing the coupling of both aliphatic and aromatic aldehydes to a variety of electron‐deficient olefins [10] . On two occasions, TBADT has been reacted with furfural where the coupling to levoglucosenone gave 7 % yield [11] while the reaction with ethyl α‐(phenylsulfonylmethyl)acrylate resulted in 59 % yield [12] . In addition, furfural has been reacted with acrylonitrile, ethyl acrylate and benzoquinone in the presence of other photocatalysts, [13] but besides these few examples, no systematic investigation has been performed on the photocatalyzed coupling between furfural and electron‐poor olefins.…”