Diastereotopos-Differentiation in the Rh-Catalyzed Amination of Benzylic Methylene Groups in the α-Position to a Stereogenic Center
作者:Anike Nörder、Sarah A. Warren、Eberhardt Herdtweck、Stefan M. Huber、Thorsten Bach
DOI:10.1021/ja3066682
日期:2012.8.15
the C-H bond, which is diastereoselectively attacked, and steric strain between the remaining substituents at the stereogenic and the prostereogenic center is minimized. DFT calculations support this model. They suggest, however, that the reaction is not concerted but occurs via hydrogen atom abstraction and subsequent radical rebound. Further support for an antiperiplanar attack relative to a given
用 18 种手性开链底物检查了 Rh 催化的 CH 胺化的非对映选择性,这些底物在立体中心 (-CHMeX) 的 α 位带有一个苄基亚甲基,以及四种手性环状四氢萘,其中立体中心位于碳原子 C2。使用三氯乙氧基磺酰基取代的胺(H(2)NTces)作为氮源,二酰氧基碘苯作为氧化剂和双[铑(α,α,α',α'-四甲基-1,3-苯二丙酸酯)] [Rh(2)(esp)(2)] 作为催化剂。对于无环底物,如果取代基 X 是 Br、PO(OEt)(2)、SO(2)Ph 或 OOCCF(3)(八个例子),则发现高顺式非对映选择性(dr > 95/5)。发现 X = NO(2)、OAc、COOMe 和 CN(八个示例)具有中等至良好的顺式选择性(dr = 80/20 至 91/9)。只有两种底物具有低的非对映选择性。动力学同位素效应 (KIE) 实验表明,用 -CDMeCOOMe 替换 -CHMeCOOMe