Upon irradiation of 3-alkyl-4-phenoxybut-1-enes 1a-d at 254 nm in cyclohexane, ortho and meta photocycloadditions occur. The ortho photocycloadducts rearrange readily, while the meta photocycloaddition involves the 2′,6′-positions of the arene as directed by the alkoxy group. In each case only a single meta photocycloadduct with an endo alkyl group is formed resulting in six contiguous stereocentres
在
环己烷中于254 nm照射3-烷基-4-苯氧基丁-1-烯1a-d后,发生邻位和间位光环加成反应。的邻photocycloadducts重新排列容易,而元光环涉及2',
芳烃的6'-位所指示的烷氧基。在每种情况下,仅形成具有内烷基的单个间位光环加合物,产生六个连续的立体中心。3-烷基基团不会显着影响模式选择性。