RESUMEN
An N-heterocyclic carbene (NHC) catalyzed intramolecular lactonization to prepare densely functionalized bicyclic γ-lactam-γ-lactone adducts from enals is reported. This method has been applied to the formal synthesis of salinosporamide A, a potent 20S proteasome inhibitor and anti-cancer therapeutic.
RESUMEN
A new synthetic approach to chiral imidazolium salts makes possible the first synthesis of an N-mesityl substituted, aminoindanol-derived N-heterocyclic carbene precursor, 1.ClO4. The successful synthesis allows the first direct comparison of otherwise identical imidazolium and triazolium precursors across a number of NHC-catalyzed processes. These studies confirm striking differences in reactivity and mechanism between the two classes.
Asunto(s)
Imidazoles/síntesis química , Catálisis , Imidazoles/química , Indicadores y Reactivos/química , Estructura Molecular , Sales (Química) , EstereoisomerismoRESUMEN
Highly enantioselective, N-heterocyclic carbene (NHC)-catalyzed aza-Diels-Alder reactions are described. A novel chiral triazolium salt based on the cis-1,2-aminoindanol platform serves as an efficient precatalyst for the NHC-catalyzed redox generation of enolate dienophiles that undergo LUMOdiene-controlled Diels-Alder reactions with N-sulfonyl-alpha,beta-unsaturated imines in good yields and with exceptional diastereo- and enantioselectivities (>99% ee). In contrast to uncatalyzed variants, this organocatalytic process proceeds at room temperature without stoichiometric reagents, producing synthetically valuable, enantiomerically pure cis-3,4-disubstituted dihydropyridinone products.