Synthesis of chiral chromans by the Pd-catalyzed asymmetric allylic alkylation (AAA): Scope, mechanism, and applications
Synthesis of chiral chromans by the Pd-catalyzed asymmetric allylic alkylation (AAA): Scope, mechanism, and applications
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DOI：
10.1021/ja048078t
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发表时间：
2004-09-29
影响因子：
15
通讯作者：
Sylvain, C
中科院分区：
文献类型：
--
作者：
Trost, BM;Shen, HC;Sylvain, C
钯催化的苯酚烯丙基碳酸酯的不对称烯丙基烷基化反应是一种有效的构建烯丙基C-O键的策略，可获得ee值高达98%的手性苯并二氢吡喃.详细研究了pH值、烯烃几何构型以及取代方式对手性苯并二氢吡喃的ee值和绝对构型的影响.这些观察结果表明一种机制，涉及环化反应性更强的π-烯丙基钯非对映体中间体作为对映体区分步骤（Curtin-Hammett条件）。这种方法导致了维生素E核心的对映选择性合成，（+）-clusifoliol和（-）-siccanin的第一个对映选择性全合成，以及（+）-rhodododaurichromanic acid A的高级中间体的合成。
The Pd-catalyzed asymmetric allylic alkylation (AAA) of phenol allyl carbonates serves as an efficient strategy to construct the allylic C-O bond allowing access to chiral chromans in up to 98% ee. The effect of pH and the influence of olefin geometry, as well as substitution pattern on the ee and the absolute configuration of the chiral chromans were explored in detail. These observations suggest a mechanism involving the cyclization of the more reactive pi-allyl palladium diastereomeric intermediate as the enantiodiscriminating step (Curtin-Hammett conditions). This methodology led to the enantioselective synthesis of the vitamin E core, the first enantioselective total synthesis of (+)-clusifoliol and (-)-siccanin, and the synthesis of an advanced intermediate toward (+)-rhododaurichromanic acid A.