Lewis acid-promoted oxidative addition of thioimidates to Pd0.
Lewis acid-promoted oxidative addition of thioimidates to Pd0.
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DOI：
10.1021/jo026510o
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发表时间：
2002-11
期刊：
影响因子：
--
通讯作者：
I. Ghosh;P. Jacobi
中科院分区：
文献类型：
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作者：
I. Ghosh;P. Jacobi
在Pd(0)催化的交叉偶联反应中，同分异构体S甲基二氢吡咯9-Z和9-E表现出明显不同的行为。使用Pd(0)/AlkZnI，硫代亚胺9-Z很容易转化为亚胺10-Z。在相同的条件下，9-E是惰性的。Pd(0)的氧化加成需要锌或其他Lewis酸的活化，这在空间上不利于9-E。相关的硫代亚胺化合物11-E、Z和甲基硫代吡啶19α-伽马也得到了类似的结果。在11和19的情况下，在BF(3)x Et(2)O的存在下，极大地促进了Pd(0)的氧化加成。在这种底物中，Lewis酸活化对Pd(0)氧化加成的重要性似乎是一个以前没有认识到的普遍现象。
The isomeric S-methyldihydropyrrins 9-Z and 9-E exhibit markedly different behavior in Pd(0)-catalyzed cross-coupling reactions. Thioimidates 9-Z are readily converted to imines 10-Z employing Pd(0)/AlkZnI. Under identical conditions 9-E are inert. Oxidative addition to Pd(0) requires activation by Zn or other Lewis acids, which is sterically unfavorable with 9-E. Analogous results were obtained with the related thioimidates 11-E,Z as well as with methylthiopyridines 19alpha-gamma. In the case of both 11 and 19 oxidative addition to Pd(0) was greatly facilitated in the presence of BF(3) x Et(2)O. The importance of Lewis acid activation to Pd(0) oxidative addition in such substrates appears to be a general phenomenon not previously recognized.