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The addition of a hydroxyl group to α,β-unsaturated carbonyl systems provides a new and easy access to bioactive difunctionalized sesquiterpene lactones (SLs) through a Michael addition to the α-methylene-γ-lactone system. The use of HMPA to enhance the nucleophilic properties of the hydroxyl groups and to stabilize the enolate is discussed. Also, we present a proposal for the mechanism based on the...
In the presence of excess dimethylacetylene dicarboxylate (DMAD), nickel(II) pyrrolo[3,4-b]porphyrins undergo both Diels–Alder cycloaddition and Michael addition in toluene to give two bis-adducts, identified as compounds 4 and 5; the reaction can be accelerated by the addition of Lewis or Brønsted–Lowry acids. Refluxing the reaction mixture in 1,2,4-trichlorobenzene (220°C) leads to a nickel(II)...
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