Miyabe Hideto, Yoshida Kazumasa, Yamauchi Masashige, Takemoto Yoshiji
Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.
J Org Chem. 2005 Mar 18;70(6):2148-53. doi: 10.1021/jo047897t.
[reaction: see text] The viability of hydroxylamines as nucleophiles in transition-metal-catalyzed allylic substitutions was examined. We have found that the oxygen atom of hydroxylamines having an N-electron-withdrawing substituent (also known as hydroxamic acids) acts as a reactive nucleophile. The palladium-catalyzed O-allylic substitution of hydroxylamines with allylic carbonate afforded the linear hydroxylamines. The selective formation of the branched hydroxylamines was observed in iridium-catalyzed reaction. Regio- and enantioselective allylic substitution of the unsymmetrical phosphates with hydroxylamines was studied by using the iridium complex of chiral pybox ligand. The aqueous-medium reaction with hydroxylamines proceeded smoothly in the presence of Ba(OH)(2).H(2)O to give the branched products with good enantioselectivities.
[反应：见正文] 研究了羟胺作为亲核试剂在过渡金属催化的烯丙基取代反应中的活性。我们发现，具有吸电子N取代基的羟胺（也称为异羟肟酸）的氧原子可作为活性亲核试剂。钯催化的羟胺与烯丙基碳酸酯的O-烯丙基取代反应得到线性羟胺。在铱催化的反应中观察到支链羟胺的选择性生成。使用手性吡唑啉酮配体的铱配合物研究了不对称磷酸酯与羟胺的区域和对映选择性烯丙基取代反应。在Ba(OH)₂·H₂O存在下，与羟胺的水相介质反应顺利进行，得到具有良好对映选择性的支链产物。
