Abstract
A palladium-catalyzed decarboxylative asymmetric allylic alkylation of thietane 1,1-dioxides via linear enolate intermediates from racemic starting materials has been developed. This process installs an α-sulfonyl tetrasubstituted stereogenic center with high enantioselectivity. The potential to transform the alkylated products to novel types of enantioenriched spirocycles for medicinal chemistry applications has also been demonstrated.
Highlights
A palladium-catalyzed decarboxylative asymmetric allylic alkylation of thietane 1,1-dioxides via linear enolate intermediates from racemic starting materials has been developed
The Stoltz group discovered that the Pd-DAAA reaction of linear enol carbonate 5 gives 6 with high enantioselectivity irrespective of the ratio of E/Z enol carbonates 5 due to a palladium-mediated interconversion of the intermediate enolates prior to alkylation (Scheme 1B).7h
Tunge and coworkers developed an enantiospecific, stereoretentive decarboxylative allylic alkylation of linear sulfones 7 to 8 (Scheme 1C).8b Their study revealed that allylic alkylation occurred faster than racemization of the α-sulfonyl anion, retaining the stereochemical information in the process
Summary
A palladium-catalyzed decarboxylative asymmetric allylic alkylation of thietane 1,1-dioxides via linear enolate intermediates from racemic starting materials has been developed. We illustrate the utility of these products in the synthesis of the novel, enantioenriched thietane 1,1-dioxide containing spirocycle 12. With the optimal conditions identified, the substrate scope was investigated by subjecting racemic precursors 16 and 17 to the catalytic reaction (Scheme 3).
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