Photoinduced assembly of the 3,4,4a,7a-tetrahydro-1H-cyclopenta[b]pyridine-2,7-dione core on the basis of allomaltol derivatives.

A novel photochemical method for construction of previously unknown substituted 4a,7a-dihydroxy-5-methyl-3,4,4a,7a-tetrahydro-1H-cyclopenta[b]pyridine-2,7-diones based on readily available allomaltol derivatives containing amide group was established. The proposed approach includes the photoinduced contraction of allomaltol ring and subsequent intramolecular cyclization of unstable α-hydroxy-1,2-diketone intermediate. For the first time we have shown the use of side chain amide function as trapping element for the final cyclization of photogenerated α-hydroxy-1,2-diketones. The structures of two synthesized photoproducts were determined by X-Ray diffraction