Competition Studies in Alkyne Electrophilic Cyclization Reactions
作者:Saurabh Mehta、Jesse P. Waldo、Richard C. Larock
DOI:10.1021/jo802196r
日期:2009.2.6
toward alkyneelectrophiliccyclizationreactions has been studied. The required diarylalkynes have been prepared by consecutive Sonogashira reactions of appropriately substituted aryl halides and competitive cyclizations have been performed using I2, ICl, NBS and PhSeCl as electrophiles. The results indicate that the nucleophilicity of the competing functional groups, polarization of the alkyne triple
已经研究了各种官能团对炔烃亲电环化反应的相对反应性。所需的二芳基炔已通过适当取代的芳基卤化物的连续 Sonogashira 反应制备,并使用 I 2、ICl、NBS 和 PhSeCl 作为亲电子试剂进行竞争性环化。结果表明,竞争官能团的亲核性、炔烃三键的极化和中间体的阳离子性质是决定这些反应结果的最重要因素。
Mechanistic Studies of Formal Thioboration Reactions of Alkynes
作者:Adena Issaian、Darius J. Faizi、Johnathan O. Bailey、Peter Mayer、Guillaume Berionni、Daniel A. Singleton、Suzanne A. Blum
DOI:10.1021/acs.joc.7b01500
日期:2017.8.4
boron reagent found second-order kinetics, supporting the likely relevancy of intermediates in this system to the ClBcat system. Computational studies comparing ClBcat with BCl3 as an activating agent showed why BCl3, in contrast to ClBcat, failed to mediate the complete the cyclization/demethylation reaction sequence by itself. Overall, the results support a mechanism in which the ClBcat reagent serves
最近已报道了几种正式的杂环基环化反应,但鲜为人知的物理-有机和机械数据。现在,我们研究炔烃的无催化剂形式硫代硼酸酯化反应,以获得对B-氯邻苯二甲硼烷(ClBcat)的机械洞察力,它在亲电性环化/脱烷基反应中作为亲核性路易斯酸发挥了新的作用。在动力学研究中,相对于2-炔基硫代苯甲醚底物和ClBcat亲电子试剂,该反应是整体二级反应,在90°C时活化参数为ΔG ‡ = 27.1±0.1 kcal mol –1,Δ H ‡ = 13.8±1.0 kcal mol –1和ΔS ‡= −37±3 cal mol –1 K –1,在70–90°C的范围内测得。碳动力学同位素效应支持决定速率的Ad E 3机理,其中中性ClBcat的炔烃激活与亲核硫的环化攻击相协调。Hammett的一项研究发现ρ +为-1.7,这表明在环化过程中阳离子电荷积聚,并支持确定速率的协同环化过程。与三(五氟苯基)硼烷(B(C 6
Catalyst-Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes
作者:Darius J. Faizi、Ashlee J. Davis、Fiach B. Meany、Suzanne A. Blum
DOI:10.1002/anie.201608090
日期:2016.11.7
isolated prior to downstream functionalization. This methodology has been extended to the synthesis of borylated dihydrothiophenes. Mechanistic experiments suggest that the operative mechanistic pathway is through boron‐induced activation of the alkyne followed by electrophilic cyclization, as opposed to S−B σ bond formation, providing a mechanistically distinct pathway to the thioboration of C−C π bonds.