Ligand-Enabled, Copper-Catalyzed Regio- and Stereoselective Synthesis of Trialkylsubstituted Alkenylboronates from Unactivated Internal Alkynes
Ligand-Enabled, Copper-Catalyzed Regio- and Stereoselective Synthesis of Trialkylsubstituted Alkenylboronates from Unactivated Internal Alkynes
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DOI：
10.1021/jacs.6b04646
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发表时间：
2016-06-22
影响因子：
15
通讯作者：
Kanai, Motomu
中科院分区：
文献类型：
--
作者：
Itoh, Taisuke;Shimizu, Yohei;Kanai, Motomu
我们首次报道了铜催化的二烷基取代内炔与二（频哪醇合）二硼和卤代烷的区域和立体选择性硼烷基化反应。催化生成的硼基铜物种含有一个新的π-接受N-杂环卡宾配体与未活化的内炔在烷基卤化物上化学选择性反应。中间体烯基铜物质随后与烷基卤化物反应，得到所需产物。铜催化剂区分空间需求之间的两个脂肪族取代基上的C-C三键的炔底物表现出高的区域选择性，从宽范围的炔/卤代烷组合。该方法可用于直接合成三烷基取代的链烯基硼酸酯，即，用于含有三个或四个不同烷基取代基的四取代烯烃的通用前体，其难以通过其它方法合成。
We report the first copper-catalyzed regio- and stereoselective borylalkylation of dialkylsubstituted internal alkynes with bis(pinacolato)diboron and alkyl halides. A catalytically generated borylcopper species containing a novel a pi-accepting N-heterocyclic carbene ligand chemoselectively reacted with unactivated internal alkynes over alkyl halides. The intermediate alkenylcopper species subsequently reacted with alkyl halides, affording the desired products. The copper catalyst differentiated steric demands between the two aliphatic substituents on the C C triple bond of the alkyne substrates to exhibit high regioselectivity from a wide range of alkyne/alkyl halide combinations. This method is useful for the straightforward synthesis of trialkylsubstituted alkenylboronates, i.e., versatile precursors for tetrasubstituted alkenes containing three or four different alkylsubstituents, which are difficult to synthesize by other methods.