Primärprodukte bei den Photocycloadditionen von 9‐Anthracencarbonitril an α‐Terpinen und 1‐Methoxy‐1,3‐cyclohexadien

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Abstract
Primary Products in Photocycloadditions of 9‐Anthracenecarbonitrile to α‐Terpinene and 1‐Methoxy‐1,3‐cyclohexadieneThe title reactions proceed with high orientational selectivity according to the requirements of hybridization effects in diradical mechanisms even under the rather extreme conditions of steric hindrance and polarity involved. In competition to exciplex formation the highly hindered [4 + 2]‐ and [4 + 4]‐adducts 3, and 4 are formed via different diradicals A and B. 4 undergoes a rapid 1,3‐suprafacial shift to yield 6 at 80°C, as does 9 at 0°C to yield the enol 10 which is hydrolyzed to yield the ketone 11. The structures of the products are established primarily by high field 1H‐NMR spectroscopy.