Construction of Spiro-γ-butyrolactone Core via Cascade Photochemical Reaction of 3‑Hydroxypyran-4-one Derivatives

We
elaborate a novel one-step photochemical method for the synthesis
of spiro-γ-butyrolactone derivatives from 3-hydroxypyran-4-ones.
The suggested approach is based on a cascade process including initial
photoinduced contraction of 4-pyranone ring followed by intramolecular
cyclization leading to the final spiro system. A distinctive feature
of the proposed method is intramolecular trapping of unstable α-hydroxydiketone
intermediate formed in situ as a result of a photochemical
reaction. The structures of two synthesized 1-oxaspiro[4.4]­non-8-ene-2,6,7-triones
were determined by X-ray diffraction.