Enantioselective Michael reactions. Diastereoselective reactions of chlorotitanium enolates of chiral N-acyloxazolidinones with representative electrophilic olefins
摘要:
In the present study we wish to report the details of the diastereoselective reactions of titanium enolates derived from N-propionyloxazolidone 1 in inter-and intramolecular Michael reactions with ethyl vinyl ketone, methyl acrylate, and acrylonitrile (eq 1).
Enantioselective Organocatalytic Michael Additions of Aldehydes to Enones with Imidazolidinones: Cocatalyst Effects and Evidence for an Enamine Intermediate
作者:Timothy J. Peelen、Yonggui Chi、Samuel H. Gellman
DOI:10.1021/ja0532584
日期:2005.8.24
An enantioselective intermolecular Michaeladdition of aldehydes to enones catalyzed by imidazolidinones has been achieved. Chemoselectivity (Michaeladdition vs aldol) can be controlled through judicious choice of hydrogen-bond-donating cocatalysts. The optimal imidazolidinone/hydrogen-bond-donor pair affords Michaeladdition products in excess of 90% ee. Furthermore, we have isolated and characterized
已经实现了醛与由咪唑烷酮催化的烯酮的对映选择性分子间迈克尔加成。化学选择性(迈克尔加成与羟醛)可以通过明智地选择供氢键的助催化剂来控制。最佳咪唑烷酮/氢键供体对提供超过 90% ee 的迈克尔加成产物。此外,我们已经分离并表征了烯胺中间体,并证明了其在观察到的迈克尔加成反应中作为亲核试剂的功效。
Titanium chloride-mediated reactions of the silyl ketene acetals derived from N-methylephedrine esters: an asymmetric variant of the Mukaiyama reaction