Photochemical High-yield Preparation of Tricyclo [3.3.0.02,8]octan-3-ones. Potential Synthons for Polycyclopentanoid Terpenes and Prostacyclin Analogs. Preliminary Communication

✍ Scribed by Martin Demuth; Palaykotai R. Raghavan; Charles Carter; Koichi Nakano; Kurt Schaffner

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: German
• Weight: 362 KB
• Volume: 63
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19800630836

✦ Synopsis

Abstract

Three‐step syntheses and the resolution into the enantiomers are reported for the tricyclo[3.3.0.0^2,8^]octan‐3‐ones 7–9, which are destined to serve as synthons for polycyclopentanoid terpenes and prostacyclin analogs. Routine overall yields of ca. 75% for 7, 40% for 8, and 46% for 9 are obtained, with 2‐chloroacrylonitrile and 1,3‐cyclohexadiene (for 7) and 1‐methyl‐1,4‐cyclohexadiene (for 8 and 9) as the starting materials. The key step is the triplet‐sensitized oxadi‐π‐methane photorearrangement of the β,γ‐unsaturated ketones 1–3 which can be achieved in 80–90% yields of isolated product and quantum yields of 0.5–1.0. The racemates of both ketone 1 and its photoisomer 7 have been resolved via chromatographic separation of suitable diastereoisomeric acetal mixtures. On the other hand, sensitization of 1 with an optically active donor, (‐)‐14, gave only an impractical maximum enantiomeric excess of 10% (‐)‐7.