Photochemistry of Arylidene-<i>β</i>-ionones: A Highly Efficient Route to Novel Tricyclic Ketones through Intramolecular, Exoselective Photochemical (4 + 2) Cycloadditions, Occurring Only in an Aqueous−Organic Solvent
作者:Mohan Paul S. Ishar、Rajinder Singh、Kamal Kumar、Gurmit Singh、D. Velmurugan、A. Subbiah Pandi、S. S. Sundra Raj、H. K. Fun
DOI:10.1021/jo010963w
日期:2002.4.1
5-dienes (3a-f, approximately 90%) by irradiating in anhydrous solvents. Irradiation of (3a-f) in aqueous methanol results in Z,E-arylidene-beta-ionones (2), through retro-electrocyclization, which undergoes an intramolecular, exo-selective [4 + 2] photocycloaddition leading to 11-(exo)-aryl-1,7,7-trimethyl-tricyclo[4.4.0.1(2,4)]undec-5-ene-3-ones (8a-f, 60-80%). The latter rearrange over silica gel
(E,E)-亚芳基-β-紫罗兰酮(1a-f)被转化为1,7,7-三甲基-3-(E-2'-芳基乙烯基)-2-氧杂双环[4.4.0] deca-3,通过在无水溶剂中辐照,可生成5-二烯(3a-f,约90%)。(3a-f)在甲醇水溶液中的辐照导致Z,E-亚芳基-β-紫罗兰酮(2)通过逆电环化作用进行分子内,选择性外[4 + 2]光环加成反应,生成11-(exo )-芳基-1,7,7-三甲基三环[4.4.0.1(2,4)]十一-5-烯-3-酮(8a-f,60-80%)。后者在硅胶上重排,以定量得到5-芳基-7,11,11-三甲基-三环[5.4.0.0(3,6)]十一烷基-1-烯-4-酮(5a-f)。在甲醇水溶液中辐照1a-f会导致8a-f,但在1c,f的情况下,其中分别形成了三环酮9c(55%)和9f(80%)的三环酮,这种三环酮是由2的光去共轭衍生而来的,