Rapid access to pyrazolo[3,4-c]pyridines via alkyne annulation:: Limitations of steric control in nickel-catalyzed alkyne insertions
Rapid access to pyrazolo[3,4-c]pyridines via alkyne annulation:: Limitations of steric control in nickel-catalyzed alkyne insertions
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DOI：
10.1021/ol701784w
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发表时间：
2007-11-22
期刊：
影响因子：
5.2
通讯作者：
Natarajan, Swaminathan R.
中科院分区：
文献类型：
--
作者：
Heller, Stephen T.;Natarajan, Swaminathan R.
多官能化的吡唑并[3，4-c]吡啶容易地通过炔与叔丁基4-碘吡唑并羧肟的环化来制备。发现该反应被NiBr 2（PPh 3）（2）/Zn或PdCl 2（PhCN）（2）催化，以良好至中等产率产生复杂的杂环。发现使用镍催化的环化是区域随机的，这意味着基于预插入络合物中的Ni-C键的特征，在镍催化的炔插入中的空间控制具有局限性。
Polyfunctionalized pyrazolo[3,4-c]pyridines ere readily prepared by the annulation of alkynes with tert-butyl 4-iodopyrazolocarboximines. The reaction was found to be catalyzed by both NiBr2(PPh3)(2)/Zn or PdCl2(PhCN)(2) to yield complex heterocycles in good to moderate yields. Annulation using nickel catalysis was found to be regio-random, implying that steric control in nickel-catalyzed alkyne insertion has limitations based on the character of the Ni-C bond in the pre-insertion complex.