Trost Barry M, Thaisrivongs David A
Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
J Am Chem Soc. 2009 Sep 2;131(34):12056-7. doi: 10.1021/ja904441a.
We report a new method for the highly regio-, diastereo-, and enantioselective palladium-catalyzed allylic alkylation of 2-substituted pyridines that allows for the formation of homoallylic stereocenters containing alkyl, aryl, heteroaryl, and nitrogen substituents. When the reaction is conducted with asymmetric acyclic electrophiles, both linear and branched products may be obtained exclusively by selecting the appropriate regioisomeric starting material and ligand, an example of the "memory effect." Deuterium-labeling studies reveal that though no such phenomenon occurs with racemic cyclic electrophiles, the chiral ligand employed reacts kinetically faster with the enantiomer of the substrate for which it is "matched" and yet eventually converts all "mismatched" substrate to product.
我们报道了一种用于2-取代吡啶的高度区域选择性、非对映选择性和对映选择性钯催化烯丙基烷基化的新方法，该方法能够形成含有烷基、芳基、杂芳基和氮取代基的高烯丙基立体中心。当使用不对称非环状亲电试剂进行反应时，通过选择合适的区域异构体起始原料和配体，可以仅获得线性和支链产物，这是“记忆效应”的一个例子。氘标记研究表明，虽然外消旋环状亲电试剂不会出现这种现象，但所使用的手性配体与它“匹配”的底物对映体反应动力学更快，但最终仍会将所有“不匹配”的底物转化为产物。
