Ma Shengming, Zhang Aibin
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P. R. China.
J Org Chem. 2002 Apr 5;67(7):2287-94. doi: 10.1021/jo0111098.
Two different types of coupling patterns for the Pd(0)-catalyzed coupling reaction of allenic/propargylic zinc reagents with organic halides or propargylic carbonates (acetate) with the corresponding organometallic reagents were observed. After studying the controlling factors on the regioselectivity of this reaction, we demonstrated that the steric hindrance of both reactants and the types of organic halides determine the regioselectivity of this coupling reaction. By subtle choosing of the substrates, the regioselectivity can be tuned. On the basis of these results, new methodologies for the highly regio- and stereoselective synthesis of 6-substituted hex-5-yn-2-enoates and 4,6-dialkylhexa-2,4,5-trienoates have been developed. Some of the products synthesized by the carbonate protocol cannot be prepared by the lithiation protocol because the regioselectivity of lithiation of dialkyl-substituted internal alkynes is an intrinsic problem.
观察到了两种不同类型的偶联模式，即钯(0)催化的联烯型/炔丙基锌试剂与有机卤化物的偶联反应，以及炔丙基碳酸酯(乙酸酯)与相应有机金属试剂的偶联反应。在研究了该反应区域选择性的控制因素后，我们证明了两种反应物的空间位阻和有机卤化物的类型决定了该偶联反应的区域选择性。通过巧妙选择底物，可以调节区域选择性。基于这些结果，已经开发出了用于高区域和立体选择性合成6-取代己-5-炔-2-烯酸酯和4,6-二烷基己-2,4,5-三烯酸酯的新方法。一些通过碳酸酯方法合成的产物不能通过锂化方法制备，因为二烷基取代的内炔锂化的区域选择性是一个固有问题。
