An Organocatalytic Oxidative Coupling Strategy for the Direct Synthesis of Arylated Quaternary Stereogenic Centers
摘要:
A broadly applicable oxidative coupling strategy of 3-substituted catechols and carbon-centered pro-nucleophiles for the construction of arylated quaternary stereogenic centers has been developed. Pivoting on a base-catalyzed addition of a carbon-centered acid to an in situ generated o-benzoquinone, the method is general and atom-economical and provides remarkably efficient access to one of the most challenging structural motifs. Furthermore, use of chiral bifunctional organocatalysts allows the process to be rendered asymmetric (up to 81% ee).
The reaction of electrochemically generated o-benzoquinones (2a-f) as Michael acceptors with 2-acetylcyclohexanone (ACH) and 2-acetylcyclopentanone (ACP), as nucleophiles has been studied in various pHs using cyclic voltammetry. The results indicate that the participation of o-benzoquinones (2a-f) in the Michaelreaction with acetylcyclohexanone (ACH) to form the corresponding catechol derivatives
An Organocatalytic Oxidative Coupling Strategy for the Direct Synthesis of Arylated Quaternary Stereogenic Centers
作者:Katherine M. Bogle、David J. Hirst、Darren J. Dixon
DOI:10.1021/ol702277v
日期:2007.11.1
A broadly applicable oxidative coupling strategy of 3-substituted catechols and carbon-centered pro-nucleophiles for the construction of arylated quaternary stereogenic centers has been developed. Pivoting on a base-catalyzed addition of a carbon-centered acid to an in situ generated o-benzoquinone, the method is general and atom-economical and provides remarkably efficient access to one of the most challenging structural motifs. Furthermore, use of chiral bifunctional organocatalysts allows the process to be rendered asymmetric (up to 81% ee).
An oxidative coupling for the synthesis of arylated quaternary stereocentres and its application in the total synthesis of powelline and buphanidrine
作者:Katherine M. Bogle、David J. Hirst、Darren J. Dixon
DOI:10.1016/j.tet.2010.04.132
日期:2010.8
Catechol derivatives directly bonded to all-carbon quaternary stereocentres are prevalent in nature. An oxidative coupling strategy for the synthesis of this motif is described. Pivoting on the base-catalysed Michael addition of carbon-centred pro-nucleophiles to in situ generated ortho-benzoquinones, the method is broad in scope, high yielding and provides remarkably simple access to this challenging motif. The application of this methodology in the total synthesis of the crinane-type amaryllidaceae alkaloids (+/-)-powelline and (+/-)-buphanidrine is demonstrated and our efforts towards an enantioselective synthesis described. (C) 2010 Elsevier Ltd. All rights reserved.