A catalyst and additive-free annulation of 2-pyridylacetates and ynals under molecular oxygen was the first developed, affording 3-acylated indolizines in good to excellent yields. Molecular oxygen was used as the source of the carbonyl oxygen atom in indolizines. This approach was compatible with a wide range of functional groups, and especially it has been successfully extended to unsaturated double bonds and triple bonds, which were difficult to prepare by previous methods in a single step.

中文翻译：

---

2-吡啶基乙酸酯和Ynals与分子氧的无催化剂环合：进入3-酰化吲哚嗪的途径

最早开发出了在分子氧下无催化剂的2-吡啶基乙酸酯和乙醛环化反应的方法，可提供3-酰化的吲哚嗪类化合物，收率好至极佳。分子氧被用作吲哚嗪中羰基氧原子的来源。该方法与广泛的官能团兼容，尤其是已成功地扩展到不饱和双键和三键，这是以前的方法难以在单个步骤中制备的。