Synthetic Approaches to Hydroazulenes and Guaianes through [4 + 3] Cycloadditions of Oxyallyl Intermediates
作者:Baldur Föhlisch、Robert Flogaus、Gerhard H. Henle、Stefan Sendelbach、Sonja Henkel
DOI:10.1002/ejoc.200500777
日期:2006.5
prepared by the title reaction. 4-(3-Methylfuran-2-yl)butan-2-one (1) was obtained in five steps from methyl 3-methylfuran-2-carboxylate (4), and treatment of 1 with pentachloroacetone and sodium 2,2,3,3-tetrafluoropropoxide in 2,2,3,3-tetrafluoropropan-1-ol produced a [4 + 3] cycloadduct that was dechlorinated without prior isolation to give the oxabicyclic diketone 2 in a low yield. A better route to diketone
通过标题反应制备了合成愈创木酚和仲瓜烷倍半萜类化合物的结构单元。4-(3-甲基呋喃-2-基)丁-2-酮(1)由3-甲基呋喃-2-羧酸甲酯(4)分五步得到,1用五氯丙酮和2,2,3钠处理,3-四氟丙氧化物在 2,2,3,3-四氟丙-1-醇中生成 [4 + 3] 环加合物,无需事先分离即可脱氯,以低收率得到氧杂双环二酮 2。生成二酮 2 的更好途径是通过 oxabicycle 10b,它由 2-(but-3-en-1-yl)-3-methylfuran (9) 和五氯丙酮以高产率制备,然后进行脱氯。用稀释的甲醇氢氧化钾处理 2 导致氧杂桥的裂解,形成 3,8-二甲基 azulen-4-ol (11)。2的催化氢化得到饱和的氧杂双环二酮14,其分子内羟醛缩合得到三环15。在钯/碳催化剂存在下通过氢解裂解氧杂三环烯酮15的氧杂桥,得到6-羟基十氢azulen-4-一 16. 在三氟乙醇中用呋喃 9