A Practical Approach to 6H-Indol-6-ones Enables the Formal Synthesis of γ-Lycorane

We represented herein a two-step synthesis of 1-methyl-6H-indol-6-one which is an N-containing 6/5 fused bicyclic building blocks in Amaryllidaceae alkaloids. The key step featured is a 'one-pot' ozonolysis/reductive amination/cyclization of allylated cyclohexa-1,3-dione to give bicyclic compounds. Moreover, the formal total synthesis of natural product gamma-lycorane could be achieved through a photo-promoted cyclization/oxidation cascade reaction from the resulting bicyclic intermediate.

Automated summary

Herein, a two-step synthesis of 1-methyl-6H-indol-6-one, an N-containing 6/5 fused bicyclic building block in Amaryllidaceae alkaloids, is described. The key step involves a 'one-pot' ozonolysis/reductive amination/cyclization reaction of allylated cyclohexa-1,3-dione to yield bicyclic compounds. Furthermore, the formal total synthesis of natural product gamma-lycorane was accomplished through a photo-promoted cyclization/oxidation cascade reaction starting from the resulting bicyclic intermediate.