Department of Chemistry, University of Sheffield , Sheffield S3 7HF, U.K.
J Am Chem Soc. 2014 Jun 18;136(24):8642-53. doi: 10.1021/ja501805r. Epub 2014 Jun 3.
Significant rate enhancements in the Diels-Alder reaction of alkynes and 2-pyrones bearing a Lewis basic group are observed when a combination of alkynyltrifluoroborates and BF3·OEt2 is used. This process generates functionalized aromatic compounds with complete regiocontrol. The observed rate enhancement was studied by density functional theory methods and appears to originate from coordination of the diene substrate to a mixture of alkynylborane intermediates, followed by a Lewis acid-mediated product equilibration step. Evidence for this mechanism is presented, as is the enhanced promotion of the cycloaddition via the use of alternative Lewis acid promoters.
当使用炔基三氟硼酸盐和 BF3·OEt2 的组合时，观察到带有路易斯碱性基团的炔烃和 2-吡喃酮的 Diels-Alder 反应的显著速率增强。该过程生成具有完全区域控制的官能化芳族化合物。通过密度泛函理论方法研究了观察到的速率增强，似乎源于二烯底物与炔基硼烷中间体混合物的配位，随后是路易斯酸介导的产物平衡步骤。提出了这种机制的证据，以及通过使用替代路易斯酸促进剂来增强环加成的促进作用。
