Photoinduced Hydrogen Abstraction-coupling Reaction Mechanism of Δ⁵-Steroids with Substituted 1,4-Benzoquinones via Electron Transfer Pathways

The photochemical reaction between three Δ⁵-steroids (1-3) and a series of substituted 1,4-benzoquinones and their mechanistic study were reported. The reaction in nitrogen almosphere led to the formation of three products including the steroid-quinone coupling compound (A), 7-hydroxy derivatives of Δ⁵-steroids (B) and substituted 1, 4-hydroquinone (C). Both chemical and spectrometric evidences such as UV-Visible spectra, ESR, chemically induced dynamic nuclear polarization (CIDNP) and cyclic voltammetry (CV) verified that the title reaction underwent a predominant photoinduced electron transfer pathway via the triplet quinone.