Alkynyltrifluoroborates as Versatile Tools in Organic Synthesis: A New Route to Spiroketals
摘要:
A simple and efficient two-step approach to spiroketals is described. Key steps include the preparation of functionalized hydroxyl alpha-alkynones by ring-opening reactions of lactones with lithium alkynyltrifluoroborates followed by a palladium-catalyzed hydrogenation/spirocyclization of the prespiroketal intermediate.
Alkynyltrifluoroborates as Versatile Tools in Organic Synthesis: A New Route to Spiroketals
摘要:
A simple and efficient two-step approach to spiroketals is described. Key steps include the preparation of functionalized hydroxyl alpha-alkynones by ring-opening reactions of lactones with lithium alkynyltrifluoroborates followed by a palladium-catalyzed hydrogenation/spirocyclization of the prespiroketal intermediate.
Functionalised hydroxy alpha-alkynones were transformed to the corresponding spiroketals by a one-pot cascade consisting of palladium-catalysed hydrogenation of the triple bond, hydroxyl group deprotection and spirocyclisation under mild nonacidic conditions. The reaction does not rely upon thermodynamic control to set the configuration of the ketal stereocentre so that both the anomerically stabilised and nonstabilised isomers are similarly accessible. (c) 2005 Elsevier Ltd. All rights reserved.
A simple and efficient two-step approach to spiroketals is described. Key steps include the preparation of functionalized hydroxyl alpha-alkynones by ring-opening reactions of lactones with lithium alkynyltrifluoroborates followed by a palladium-catalyzed hydrogenation/spirocyclization of the prespiroketal intermediate.