Department of Chemistry, University of Rochester , Rochester, New York, United States 14627-0216.
J Am Chem Soc. 2014 Jan 8;136(1):48-51. doi: 10.1021/ja410704d. Epub 2013 Dec 16.
Epoxides are versatile intermediates in organic synthesis, but have rarely been employed in cross-coupling reactions. We report that bipyridine-ligated nickel can mediate the addition of functionalized aryl halides, a vinyl halide, and a vinyl triflate to epoxides under reducing conditions. For terminal epoxides, the regioselectivity of the reaction depends upon the cocatalyst employed. Iodide cocatalysis results in opening at the less hindered position via an iodohydrin intermediate. Titanocene cocatalysis results in opening at the more hindered position, presumably via Ti(III)-mediated radical generation. 1,2-Disubstituted epoxides are opened under both conditions to form predominantly the trans product.
环氧化物是有机合成中用途广泛的中间体，但很少用于交叉偶联反应。我们报告说，双吡啶配体镍可以在还原条件下介导功能化芳基卤化物、卤代乙烯基和乙烯基三氟甲磺酸酯与环氧化物的加成。对于末端环氧化物，反应的区域选择性取决于共催化剂的使用。碘化物共催化通过碘代醇中间体在非位阻较小的位置开环。二茂钛共催化则在位阻较大的位置开环，可能是通过 Ti(III)介导的自由基生成。在这两种条件下，1,2-二取代环氧化物均开环形成主要为反式产物。
