A direct base-mediated intramolecular carbon-oxygen bond formation has been developed without a transition-metal catalyst. In the presence of 2.0 equiv of K2CO3 in DMSO at 140 °C, the intramolecular cyclization of o-haloanilides affords benzoxazoles in high yields. A mechanism via an initial formation of a benzyne intermediate followed by nucleophilic addition to form the CâO bond has been proposed.
在不使用过渡
金属催化剂的情况下,我们开发出了一种直接由碱介导的分子内碳氧键形成方法。在
二甲基亚砜(
DMSO)中加入 2.0 等量的 K2CO3,温度为 140 °C,邻卤代
苯胺的分子内环化反应能以高产率生成
苯并恶唑。提出的机理是先形成苄基中间体,然后通过亲核加成形成 CâO 键。