Chaudhary Sandeep, Shyamlal Bharti Rajesh K, Yadav Lalit, Tiwari Mohit K, Kumar Krishan
Laboratory of Organic and Medicinal Chemistry, Department of Chemistry, Malaviya National Institute of Technology Jaipur Jawaharlal Nehru Marg Jaipur-302017 India
RSC Adv. 2018 Jun 26;8(41):23152-23162. doi: 10.1039/c8ra03926g. eCollection 2018 Jun 21.
Herein, we disclose the first example of an efficient, silver oxide nanoparticle-catalyzed, direct regioselective synthesis of 3-ylidenephthalides 11-16 and isocoumarins 17-20 sonogashira type coupling followed by substrate-controlled 5--dig or 6--dig cyclization reaction, respectively. This one pot coupling involves reaction of substituted 2-halobenzoic acid with /-substituted and -substituted terminal alkynes, which proceeded in a regioselective manner resulting in the formation of 3-ylidenephthalides or isocoumarins, respectively, in excellent yields (up to 95%) with complete Z-selectivity. This protocol features relatively broad substrate scope, mild conditions, operational simplicity, and is favourable with aromatic/alicyclic terminal alkynes. The competition experiments and gram-scale synthesis further highlight the importance and versatility of the methodology. The proposed mechanistic pathways illustrate that the regioselectivity is substantially being controlled by the substituent(s) present on the acetylenic phenyl ring.
在此，我们首次公开了一种高效的、氧化银纳米颗粒催化的、直接区域选择性合成3-亚烷基苯酞11-16和异香豆素17-20的方法，分别通过Sonogashira型偶联反应，随后进行底物控制的5-双取代或6-双取代环化反应。这种一锅法偶联反应涉及取代的2-卤代苯甲酸与α-取代和β-取代的末端炔烃的反应，该反应以区域选择性方式进行，分别以优异的产率（高达95%）和完全的Z选择性生成3-亚烷基苯酞或异香豆素。该方法具有相对较宽的底物范围、温和的条件、操作简单，并且对芳族/脂环族末端炔烃有利。竞争实验和克级合成进一步突出了该方法的重要性和通用性。所提出的机理途径表明，区域选择性基本上由炔基苯环上存在的取代基控制。
