Photoinduced hydrogen abstraction-coupling reaction mechanism of Δ5-steroids with substituted 1, 4-benzoquinones via electron transfer pathways

The photochemical reaction between three A5-steroids (1–3) and a series of substituted 1,4-benzoquinones and their mechanistic study were reported. The reaction in nitrogen atmosphere 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.