Photochemical Reactions of Enamino Ketones

• Published in: Bulletin of the Chemical Society of Japan Vol. 46; no. 8; pp. 2504 - 2511
• Main Authors: Yamada, Kazutoshi, Konakahara, Takeo, Iida, Hirotada
• Format: Journal Article
• Language: English
• Published: The Chemical Society of Japan 01.08.1973
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.46.2504

Photochemical reactions of N-aryl enamino ketones including one enone system and one divinylamine system in the molecule were examined. Photochemical behaviours of N-aryl enamino ketones differed for the tertiary and secondary amines involved. While 5,5-dimethyl-3-(N-methylanilino)cyclohex-2-en-1-one gave an oxidative cyclization product, 3-anilino-5,5-dimethyl-cyclohex-2-en-1-one gave two major products and a minor one. One of the major products was characterized as 3,3-dimethyl-5-hydroxy-3,4-dihydro-1-benzazocines by their elemental analyses and spectroscopic properties. The compounds showed 6π system pseudo aromaticity in their NMR spectra. The temperature-dependent NMR signals for gem-dimethyl protons were due to the flapping of the 8-membered ring. The reduction product with diborane was identified as 1,2,3,4,5,6-hexahydro-1-benzazocine by comparison with an authentic sample. The other major product was a ketene adduct and the minor product, a lactone.