Bouet Alexis, Deguest Geoffrey, Heller Barbara, Papamicaël Cyril, Dupas Georges, Oudeyer Sylvain, Marsais Francis, Levacher Vincent
Laboratoire de Chimie Organique Fine et Hétérocyclique, UMR 6014, IRCOF, CNRS, Université et INSA de Rouen, B.P. 08, F-76131, Mont-Saint-Aignan Cédex, France.
Org Biomol Chem. 2007 May 7;5(9):1397-404. doi: 10.1039/b701549f. Epub 2007 Mar 23.
This work reports the synthesis of new axially chiral bridged 2,2'-bipyridines 1 and pyridylmonooxazolines (pymox) 2. The potential of these new axially chiral N,N-ligands was evaluated in asymmetric catalytic cyclopropanation of styrene derivatives 22a-c with diazoesters 21a,b. While 2,2'-bipyridines 1a-c afforded the corresponding cyclopropanes 23a-f in up to 65% ee, pymoxs 2a-e gave somewhat lower enantioselectivities (up to 53% ee). Both classes of ligands produced trans-cyclopropanes 23a-f as the major isomer, although with modest diasteroselectivities (56 : 44 to 78 : 22). A structure-stereoselectivity relationship study of ligands 1 and 2 identified the chiral biaryl axis as being mostly responsible for the enantioselective performances of these ligands.
本工作报道了新型轴向手性桥连2,2'-联吡啶1和吡啶基单恶唑啉（pymox）2的合成。在苯乙烯衍生物22a - c与重氮酯21a,b的不对称催化环丙烷化反应中评估了这些新型轴向手性N,N-配体的潜力。虽然2,2'-联吡啶1a - c以高达65%的对映体过量（ee）得到相应的环丙烷23a - f，但pymox 2a - e的对映选择性略低（高达53% ee）。两类配体均以反式环丙烷23a - f作为主要异构体，尽管非对映选择性适中（56 : 44至78 : 22）。对配体1和2的结构 - 立体选择性关系研究表明，手性联芳基轴是这些配体对映选择性表现的主要原因。
