Furan fused gamma-lactones, specifically 2,6-dioxabicyclo[3.3.0]octan-3-ones, are a prevailing structural feature in a number of biologically active natural products, including the plakortones, pallambin A, and rubriflordilactone B. The prevalence and congested complexity of this core structure call for new, efficient methods for its construction. A combined Lewis acid/photoredox catalyst system has enabled the umpolung addition of ketyl radicals to vinylogous carbonates in the synthesis of 2,6-dioxabicyclo[3.3.0]octan-3-ones. This reaction proceeded on a variety of aromatic ketones to provide THF rings in good yield (70%). Although diastereoselectivity was found to be modest for the carbon-carbon bond forming reaction, the minor diastereomers were converted to 2,6-dioxabicyclo[3.3.0]octan-3-ones by an efficient Lewis acid-mediated epimerization cascade.

Dual Lewis acid/photoredox-catalyzed addition of ketyl radicals to vinylogous carbonates in the synthesis of 2,6-dioxabicyclo[3.3.0]octan-3-ones

256th National Meeting (2018)

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