Theoretical Support for the Involvement of a Radical Pathway in the Formation of Allenylzincs from Propargyl Iodides and Dialkylzincs: Influence of Zinc Coordination
作者:Suribabu Jammi、Dominique Mouysset、Didier Siri、Michèle P. Bertrand、Laurence Feray
DOI:10.1021/jo302704g
日期:2013.2.15
undergo homolytic substitution at zinc. The stabilization of allenylzinc derivatives by chelation, made possible by the selection of appropriate ortho-substituted 3-phenylalkynyl iodides as precursors, was shown to influence the regioselectivity of their addition to aldehydes and ketones. The more stabilized the chelated allenylzinc intermediate, the higher the ratio of homopropargylic alcohols.
通过与二乙基锌反应,炔丙基碘是烯丙基锌的良好前体,即使在未脱气的介质中也是如此。这些反应通过锌/碘交换进行。由于先前报道的通过ESR实验检测到的炔丙基自由基,在此过程中怀疑存在自由基机理。用CBS-QB3方法计算了烯丙基和炔丙基锌物种中的C-Zn BDEs,以证明炔丙基可以在锌上发生均溶取代。通过选择合适的邻位取代的3-苯基炔基碘化物作为前体,可以实现螯合作用使烯丙基锌衍生物稳定化,这会影响它们加成醛和酮的区域选择性。螯合的烯丙基锌中间体越稳定,均丙醇的比例越高。