Palladium-catalyzed additions of terminal alkynes to acceptor alkynes
Palladium-catalyzed additions of terminal alkynes to acceptor alkynes
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DOI：
10.1021/ja9624937
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发表时间：
1997-01-29
影响因子：
15
通讯作者：
Ruhter, G
中科院分区：
文献类型：
--
作者：
Trost, BM;Sorum, MT;Ruhter, G
其中产物是反应物加上任何其他物质（仅需要催化）的简单总和的加成反应的发展构成了提高合成效率的重要目标。在催化量的乙酸钯和富电子空间位阻配体三（2，6-二甲氧基苯基）膦的存在下，末端炔（供体炔）的C-H键可以加到末端炔（自偶联）或活化的内部炔（交叉偶联）（受体炔）上。用于交叉偶联的活化的内部炔（受体炔）包括带有酯、砜和酮的炔。自偶联完全被交叉偶联所压倒，甚至在供体和受体炔的比例为1：1时。该反应表现出非凡的化学选择性与游离甲醛，醇，酮（饱和和共轭），酯（饱和和共轭），砜（饱和和共轭），丙二酸酯，和甲硅烷基醚都证明是兼容的。还可以优化1：2供体/受体炔加合物。丙炔酸乙酯不能作为受体，但其C-甲硅烷基化的类似物与甲硅烷基取代基的适当选择。后者的产物用作β-酮酯的有用前体。迭代序列很容易进行，并导致一种新的构象刚性类维生素A类似物。讨论了这种温和的合成共轭烯炔的方法的机理。
The development of addition reactions wherein the product is the simple sum of the reactants plus anything else (only needed catalytically) constitutes an important goal for enhanced synthetic efficiency. The C-H bond of terminal alkynes (the donor alkynes) can be added to either terminal alkynes (self-coupling) or activated internal alkynes (cross-coupling) (the acceptor alkynes) in the presence of a catalytic amount of palladium acetate and an electron rich sterically encumbered ligand, tris(2, 6-dimethoxyphenyl)phosphine. The activated internal alkynes for cross-coupling (the acceptor alkyne) include alkynes bearing an ester, sulfone, and ketone. Self-coupling is completely overwhelmed by cross-coupling, even at 1:1 ratios of donor and acceptor alkynes. The reaction exhibits extraordinary chemoselectivity with free carboxaldehydes, alcohols, ketones (saturated and conjugated), esters (saturated and conjugated), sulfones (saturated and conjugated), malonates, and silyl ethers all proving to be compatible. A 1:2 donor/acceptor alkeyne adduct can also be optimized. Ethyl propiolate fails as an acceptor but its C-silylated analogue serves with the proper choice of silyl substituent. The products of the latter serve as useful precursors to P-keto esters. An iterative sequence is readily performed and led to a novel conformationally rigid retinoid analogue. The mechanism of this mild method for construction of conjugated enynes, versatile building blocks, is discussed.