The acid-catalyzed cyclization of 2-phenylsulfonyl-4,8-dimethyi-3,7-nonadienoic acid (5) was performed by treatment with sulfuric acid-acetic acid and/or boron trifluoride in various aprotic solvents to afford 2,2,6-trimethyl-9-phenylsulfonyl-7-oxabicyclo[4.3.0]nonan-8-one (4) in 70–75% yield. Similarly, 2-phenylsulfonyl-2-(2,6,6-trimethyl-1,3-cyclohexadienyl)acetic acid provided 2,2,6-trimethyl-9
2-
苯磺酰基-4,8-二
甲基-3,7-壬二
烯酸 (5) 的酸催化环化反应是通过在各种非质子溶剂中用
硫酸-
乙酸和/或
三氟化硼处理得到
2,2, 6-trimethyl-9-phenylsulfonyl-7-oxabicyclo[4.3.0]nonan-8-one (4),产率 70–75%。类似地,2-
苯基磺酰基-2-(2,6,6-三
甲基-
1,3-环己二烯基)
乙酸提供
2,2,6-三
甲基-9-
苯基磺酰基-7-
氧杂双环[4.3.0]non-4- en-8-一 (7) 的产率为 62%。内
酯4a、4b和7被转化为二
氢actinidiolide、四
氢actinidiolide和4,5-二
氢actinidiolide。讨论了5环化的反应条件和机理。