Scope and Limitations of the Scandium-Catalyzed Enantioselective Addition of Chiral Allylboronates to Aldehydes
作者:Dennis G. Hall、Michel Gravel、Hugo Lachance、Xiaosong Lu
DOI:10.1055/s-2004-822359
日期:——
Scandium triflate catalyzes the addition of camphor-derived allyl-, methallyl-, and crotylboronates to aldehydes to provide homoallylic alcohols with excellent diastereo- and enantioselectivity. Aromatic, aliphatic, and propargylic aldehydes can be used successfully in this system. Additional advantages of the camphor-diol allylboronates are their ease of synthesis, their availability in both enantiomeric forms, and their stability towards silica gel chromatography. The usefulness of this methodology is further demonstrated by the gram-scale synthesis of various homoallylic alcohols of high enantiomeric excess and by the concise synthesis of the pheromone (4S)-2-methyloctan-4-ol.
Synthetic studies toward the pyran core and the amide side chain of psymberin
作者:Hugo Lachance、Olivier Marion、Dennis G. Hall
DOI:10.1016/j.tetlet.2008.07.170
日期:2008.10
A synthetic approach to the polysubstituted pyran core and amide side chain of psymberin (irciniastatin A) using stereoselective organoboron methodology is described. An advanced oxyranyl pyran intermediate was prepared using a catalytic enantioselective and diastereoselective three-component reaction involving first an inverse electron-demand hetero [4+2] cycloaddition between 3-boronoacrolein pinacolate and 1-ethoxy-2-methylpropene, followed by an allylboration of ethyl glyoxylate. The amide side chain was prepared highly efficiently using the first example of a doubly diastereoselective allylboration of a chiral alpha-alkoxy aldehyde under the Lewis acid-catalyzed reaction manifold. (C) 2008 Elsevier Ltd. All rights reserved.
Scandium-Catalyzed Allylboration of Aldehydes as a Practical Method for Highly Diastereo- and Enantioselective Construction of Homoallylic Alcohols
作者:Hugo Lachance、Xiaosong Lu、Michel Gravel、Dennis G. Hall
DOI:10.1021/ja036807j
日期:2003.8.1
A general approach for the allylation of aldehydes using stable, air-tolerant camphor-based chiralallylboronates under Sc(OTf)3 catalysis is described. This practical methodology provides both syn and anti propionate units and other homoallylic alcohols with very high levels of diastereo- and enantioselectivity for several substrates, including functionalized aliphatic aldehydes useful toward the