RESUMEN
Asymmetric allylic alkylation mediated by transition metals provides an efficient strategy to form quaternary stereogenic centers. While this transformation is dominated by the use of second- and third-row transition metals (e.g., Pd, Rh, and Ir), recent developments have revealed the potential of first-row transition metals, which provide not only a less expensive and potentially equally efficient alternative but also new mechanistic possibilities. This review summarizes examples for the assembly of quaternary stereocenters using prochiral allylic substrates and hard, achiral nucleophiles in the presence of copper complexes and highlights the complementary approaches with soft, prochiral nucleophiles catalyzed by chiral cobalt and nickel complexes.
Asunto(s)
Compuestos Alílicos/síntesis química , Complejos de Coordinación/química , Elementos de Transición/química , Alquilación , Catálisis , Ligandos , Solventes/química , Estereoisomerismo , Relación Estructura-Actividad , TemperaturaRESUMEN
Efforts directed toward the synthesis of a basiliolide/transtaganolide model system are disclosed. A highly endo-selective intramolecular pyrone Diels-Alder (IMPDA) cycloaddition rapidly constructs the tricyclic core of the basiliolides and transtaganolides.
Asunto(s)
Productos Biológicos/síntesis química , Compuestos Heterocíclicos de Anillo en Puente/síntesis química , Modelos Moleculares , Tapsigargina/análogos & derivados , Tapsigargina/síntesis química , Productos Biológicos/química , Productos Biológicos/clasificación , Ciclización , Compuestos Heterocíclicos de Anillo en Puente/química , Estructura Molecular , Plantas Medicinales/química , Pironas/química , Estereoisomerismo , Thapsia/química , Tapsigargina/químicaRESUMEN
[reaction: see text] A highly diastereoselective single-step cyclization reaction provides access to the bicyclo[3.3.1]nonane core of the polyprenylated phloroglucin natural product garsubellin A. Further elaboration to a more functionalized analogue involves a sequential Claisen rearrangement/Grubbs olefin cross-metathesis strategy. Additionally, this strategy was extended to the preparation of the bis-quaternary carbon array found at the bridgehead positions of the phloroglucin natural products.