Mechanistic Evaluation of the Ni(IPr)<sub>2</sub>-Catalyzed Cycloaddition of Alkynes and Nitriles To Afford Pyridines: Evidence for the Formation of a Key η<sup>1</sup>-Ni(IPr)<sub>2</sub>(RCN) Intermediate
作者:Ryan M. Stolley、Hung A. Duong、Janis Louie
DOI:10.1021/om400666k
日期:2013.9.9
Ni(IPr)2-catalyzed [2 + 2 + 2] cycloaddition of diynes and nitriles was conducted. Through kinetic analysis of these reactions, observed regioselectivities of the products, and stoichiometric reactions, Ni(IPr)2-catalyzed cycloadditions of diynes and nitriles appear to proceed by a heterooxidative coupling mechanism, in contrast to other common cycloadditioncatalysts. Reaction profiles demonstrated
对 Ni(IPr) 2催化的二炔和腈的 [2 + 2 + 2] 环加成进行了详细的机理评估。通过对这些反应的动力学分析、观察到的产物区域选择性和化学计量反应,与其他常见的环加成催化剂相比,Ni(IPr) 2催化的二炔和腈的环加成似乎是通过杂氧化偶联机制进行的。反应曲线显示出对腈的强烈依赖性,导致可变的腈依赖性静息状态。卡宾配体的强配位和相当大的空间体积有利于腈的选择性初始结合,从而形成异偶联途径。原位 IR 数据表明腈的初始结合位于罕见的 η 1结合构象。腈配位之后是腈的速率决定性触觉变化和随后的卡宾损失。炔烃配位然后导致杂氧化偶联、侧链炔烃的插入和还原消除以提供吡啶产物。
Iron-Catalyzed Cycloaddition Reaction of Diynes and Cyanamides at Room Temperature
作者:Chunxiang Wang、Dongping Wang、Fen Xu、Bin Pan、Boshun Wan
DOI:10.1021/jo400057t
日期:2013.4.5
An iron-catalyzed [2 + 2 + 2] cycloaddition reaction of diynes and cyanamides at room temperature is reported. Highly substituted 2-aminopyridines were obtained in good to excellent yields with high regioselectivity. Insights toward the reaction process were investigated through in situ IR spectra and control experiments. In this iron-catalyzed cycloaddition reaction, the active iron species was generated only in the presence of both alkynes and nitriles. The lower reaction temperature, broad substrates scope, and inversed regioselectivity make it a complementary method to the previously developed iron catalytic system.