4-Chloroisocoumarins can be conveniently prepared from 2-alkynylaryloate esters via the activation of alkynes by electrophilic chlorine, generated in situ from N-chlorosuccinimide (NCS) in the presence of 10 mol % trimethylsilyl chloride (TMSCl), which leads to 6-endo-dig-selective chlorinative annulation to give the desired products in moderate to quantitative yields. The procedure employs readily
A bromide salt mediated neighboring ester-participated bromocyclization of o-alkynylbenzoates is described here for synthesis of benzil-o-carboxylate. 4-bromoisocoumarins are also reached when phenyl o-alkynylbenzoate is used as the substrate. Mechanism studies suggest that the whole process is comprised by electrophilic bromocyclization and dibromohydration-based ring-opening, and the neighboring
Treatment of methyl2-alkynylbenzoates with two to three equivalents of CuX 2 (X = Cl or Br) in refluxing acetonitrile gave isocoumarins 2 in good to excellent chemical yields.
NBS-Mediated Oxygen Transfer Reaction of Carbonyl in Ester: Efficient Synthesis of Benzil-<i>o</i>
-carboxylate Derivative From <i>o</i>
-Alkynylbenzoate
diketonization. A plausible mechanism suggests that a bromo‐incoporated isocoumarin cation is described as an intermediate, and the whole process is constituted by NBS‐mediated electrophilic 6‐endo annulation and oxygen transferreaction through NBS‐mediated oxidative ring‐opening. Water serves as a nucleophile of ring‐opening.
One-pot synthesis of 2-(quinoxalin-2-yl)benzoate through NBS-mediated sequential reaction of 2-alkynylbenozate and aryl-1,2-diamine
作者:Bin Huang、Lele Ma、Guanyinsheng Qiu
DOI:10.1016/j.tetlet.2017.04.063
日期:2017.5
A metal-free route involving a sequential reaction of 2-alknylbenzoate and aryl-1,2-diamine is described for the generation of 2-(quinoxalin-2-yl)benzoate. The sequential reaction combines NBS-mediated diketonization of 2-alknylbenzoate and condensation reaction with aryl-1,2-diamine, and proceeds smoothly under mild reaction conditions and an array of 2-(quinoxalin-2-yl)benzoate is achieved with high