Photochemical Synthesis of Tetrahydro‐6H‐cyclopenta[b]furan‐6‐ones from Substituted Allomaltols

Abstract

A novel UV‐mediated approach for the synthesis of previously unknown 3a,6a‐dihydroxy‐4‐methyl‐2,3,3a,6a‐tetrahydro‐6H‐cyclopenta[b]furan‐6‐one derivatives from easily accessible substituted allomaltols containing a 2‐aryl‐2‐hydroxyethyl fragment was elaborated. The suggested method is based on the ESIPT‐promoted contraction of a 3‐hydroxy‐4‐pyranone moiety followed by intramolecular trapping of a photogenerated α‐hydroxy‐1,2‐diketone intermediate. For the first time, we have demonstrated that a side chain hydroxyl group can be employed for the concluding cyclization with a labile α‐hydroxy‐1,2‐diketone fragment. The structure of one synthesized photoproduct was determined by X‐ray diffraction.

Anionic photochemical rearrangement of 3-hydroxypyran-4-ones bearing oxazol-2-one fragment

“…Previously, the photochemical behavior of various terarylenes containing a 3-hydroxypyran-4-one fragment was widely studied by our group. 10 It was shown that two directions of phototransformation are possible for compounds of this class: ESIPT-induced contraction of the pyranone ring leading to unstable α-hydroxy-1,2-diketones and 6π-electrocyclization of the 1,3,5-hexatriene system. For example, upon irradiation at 365 nm, the two above-mentioned photoreactions are realized for oxazolone derivatives 1 , resulting in a complex mixture of photoproducts.…”

Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

“…This phototransformation is initiated by an excited state intramolecular proton transfer (ESIPT) process. In most cases the resulting α-hydroxy-1,2-diketones are unstable and their further reactions open access to various original products [16][17][18][19][20]. The photochemical behavior of terarylenes containing an allomaltol fragment deserves special attention.…”