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Photocyclisierungen von 1, 1'-Polymethylen-di-2-pyridonen. 46. Mitteilung über Photoreaktionen

✍ Scribed by Yushin Nakamura; Janos Zsindely; Hans Schmid

Publisher
John Wiley and Sons
Year
1976
Tongue
German
Weight
903 KB
Volume
59
Category
Article
ISSN
0018-019X

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✦ Synopsis

Photocyclization of 1, 1′‐Polymethylene‐di‐2‐pyridones.

Benzophenone sensitized irradiation of the four dipyridones 1‐4 gave the internal photocyclization products 6 (64%, Scheme 4), 7 (60%, Scheme 5), 8 (Scheme 6), and 11 (26%, Scheme 7), respectively. The decamethylene compound 5 yielded only polymeric material.

The primary [2+2] photoproduct 8 from dipyridone 3 (Scheme 6) is relatively unstable. Further irradiation or heating to 65° induced a Cope rearrangement to give compound 9 which, on heating to 137°, was converted into the isomeric compound 10. This product, as well as the other photoproducts mentioned, are rearranged back to their respective starting materials upon direct irradiation with 254 nm light or by heating to higher temperatures. The various possibilities for cycloadditions of pyridones are discussed as well as the possible factors which are responsible for the highly regioselective photoreactions of the dipyridones 1–4.

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