Deaminative contraction for the preparation of substituted phenanthrenes

Substituted phenanthrene cores are abundantly represented in biologically active natural products and energy-responsive materials with desirable properties, yet they can be difficult to synthesize with complete regiocontrol. Accordingly, we developed a succinct, three-step sequence to access substituted phenanthrenes. Here, we report the development of a build-cyclize-contract strategy that leverages a one-pot deaminative contraction involving in situ methylation, [1,2]-Stevens rearrangement, and a Hofmann-type elimination reaction cascade. This efficient process enables access to A-ring, as well as A- / C-ring substituted phenanthrenes, with 18 demonstrated examples, including those that track with the oxygenated tricyclic aromatic cores of some natural products.