Enantioselective ring-contraction reactions have not been widely reported. We have developed an enantioselective ring contraction of 5,6-dihydro-2H-benzo[b][1,4]oxazocines, affording enantiomerically enriched 3,4-dihydro-2H-1,4-benzoxazine derivatives as single regioisomers. An acidic additive is necessary in order to obtain the products with good yields and enantiomeric ratios (up to 93% yield, 98:2 er). The reaction was successfully performed on a gram scale, and the products can be derivatized easily.

中文翻译：

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Pd(II)-催化对映选择性环收缩用于构建 1,4-苯并恶嗪

对映选择性环收缩反应尚未被广泛报道。我们开发了 5,6-dihydro-2 H -benzo [ b ][1,4]oxazocines 的对映选择性环收缩，提供对映体富集的 3,4-dihydro-2 H -1,4-benzoxazine衍生物作为单一区域异构体。为了获得具有良好产率和对映体比率（高达 93% 产率，98:2 er）的产品，酸性添加剂是必需的。该反应成功地进行了克级反应，产物易于衍生化。