Titanocene-Catalyzed Cascade Cyclization of Epoxypolyprenes: Straightforward Synthesis of Terpenoids by Free-Radical Chemistry
作者:José Justicia、Antonio Rosales、Elena Buñuel、Juan L. Oller-López、Mónica Valdivia、Ali Haïdour、J. Enrique Oltra、Alejandro F. Barrero、Diego J. Cárdenas、Juan M. Cuerva
DOI:10.1002/chem.200305647
日期:2004.4.2
The titanocene-catalyzed cascade cyclization of epoxypolyenes, which are easily prepared from commercially available polyprenoids, has proven to be a useful procedure for the synthesis of C(10), C(15), C(20), and C(30) terpenoids, including monocyclic, bicyclic, and tricyclic natural products. Both theoretical and experimental evidence suggests that this cyclization takes place in a nonconcerted fashion
钛茂金属催化的环氧多烯的级联环化反应很容易从市售的聚异戊二烯类化合物制备,已证明是合成C(10),C(15),C(20)和C(30)萜类化合物的有用方法,包括单环,双环和三环天然产物。理论和实验证据均表明,这种环化反应是通过离散的以碳为中心的自由基以非融合方式发生的。然而,该方法的终止步骤似乎受到一种与水有关的控制,这在自由基化学中是不常见的。催化循环是基于使用新的组合Me(3)SiCl / 2,4,6-可力丁来再生钛茂催化剂。实际上,此过程具有以下优点: