Photoaddition of polyfunctional oxycarbinyl species to conjugated enones: A ready route to versatile γ-functionalized ketones.

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

“…Thus, in the functionalization of a hex-2-enopyranosid-4-ulose, the introduced -C(OAlk) 3 group was not stable upon chromatographic purification and was converted into a −COOAlk group. 330 Turning to alcohols, the activation of the C−H bonds in the αposition with respect to the OH group was smoothly obtained through hydrogen atom abstraction by excited aromatic ketones. 9 Thus, with the aim of synthesizing building blocks useful for the preparation of analogues of glutamate and kainoids (e.g., kainic acid), the photoaddition of methanol to chiral 5(S)-5-triisopropylsiloxymethyl-N-boc-dihydropyrrole-2(5H)-one (404) has been performed in the presence of an equimolar amount of benzophenone (Scheme 125).…”

“…In some instances, trialkylorthoformates have been likewise used as radical precursors. Thus, in the functionalization of a hex-2-enopyranosid-4-ulose, the introduced -C­(OAlk) 3 group was not stable upon chromatographic purification and was converted into a −COOAlk group …”

Photocatalysis for the Formation of the C−C Bond

“…77 The reaction was also applied to sugar-derived enones, where it proceeded with comparable yields and stereoselectivity to those in the above case of R-oxy radicals (Scheme 26). 115,138 Electron-poor alkynes (e.g., methyl propiolate) were likewise effective substrates for the BP (40% mol equiv) photocatalyzed addition of (2-alkyl-)1,3-dioxolanes. 139a Indeed, by the use of acetone photocatalysis, alkylation was obtained also with nonelectrophilic sugar-derived alkenes such as enoses.…”

Unsaturated Sugars: A Rich Platform for Methodological and Synthetic Studies

“…We found this process to be a promising method for carbon-carbon bond formation in carbohydrate chemistry, and also found that reaction with substrate 74 proceeded with complete regio-and stereoselectivity [66,67,68] (Scheme 20a-e). This methodology proved its flexibility with photoinduced addition of bifunctional alcohols (Scheme 20f), acetals [69] (Scheme 20g) and aldehydes [70,71] (Scheme 20h). Subsequent work in our laboratory, allowed us to establish that alcohols possessing anhydrogen, acetals, and aldehydes undergo photochemically induced conjugate addition to a variety of conjugated enones to give 1,4-ketols, 1,4-keto acetals and 1,4-diketones, respectively.…”