Department of Chemistry, Research Institute of Natural Sciences and Center for New Directions in Organic Synthesis (CNOS), Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, South Korea.
J Am Chem Soc. 2020 Dec 9;142(49):20788-20795. doi: 10.1021/jacs.0c09783. Epub 2020 Nov 18.
A gold(I)-catalyzed enantioselective thioallylation of propiolates with allyl sulfides is described. The key mechanistic element is a sulfonium-induced Claisen rearrangement which helps minimize the allyl dissociation and render higher enantioselectivity. This protocol features remarkable scope of the allyl moiety, allowing enantiocontrolled synthesis of all-carbon quaternary centers, and exhibits exceptional functional group compatibility with many Lewis bases and π-bonds. This intermolecular variant of Claisen rearrangement forges both C-S and C-C bonds concomitantly, providing efficient access to interesting optically active organosulfur compounds which can be transformed further through the vinyl sulfide as a functional handle. The rate of the reaction was zeroth order with respect to allyl sulfides, which suggested a reversible inhibition, providing a resting state for the catalyst. The Hammett plot displayed a correlation with σ values, suggesting a turnover-limiting sigmatropic rearrangement where decreased electron-density on sulfur accelerated the rearrangement.
描述了一种金（I）催化的丙炔酸酯与烯丙基硫醚的对映选择性硫烯丙基化反应。关键的机理要素是一个𬭩诱导的 Claisen重排，它有助于最小化烯丙基的解离并提高对映选择性。该方案具有显著的烯丙基部分的范围，允许全碳季碳原子的对映控制合成，并表现出与许多路易斯碱和π键的优异的官能团兼容性。这种 Claisen 重排的分子间变体同时形成 C-S 和 C-C 键，为通过乙烯基硫醚作为功能基团提供了高效的途径，从而获得有趣的手性有机硫化合物，这些化合物可以通过进一步转化进一步转化。反应对烯丙基硫醚呈零级反应，这表明存在可逆抑制作用，为催化剂提供了一个静止状态。Hammett 图显示与 σ 值的相关性，表明限速的西格玛重排，其中硫上的电子密度降低加速了重排。
