Regiospecificity in the cyclization of 6-(1-hydroxyalkyl) geraniol derivatives. A simple route to the taxol a-ring system
摘要:
Readily available derivatives of geraniol bearing a 1-hydroxyalkyl side chain in the 6-position undergo acid-catalyzed regiospecific cyclization to form cyclogeraniol derivatives which have an interesting relation to ring A of taxol.
当用多烯处理形成溴化产物时,2,4,4,6-四溴环己基-2,5-二烯酮(TBCO)释放出溴离子。给出了TBCO与简单烯烃的反应结果。类似的溴代酮(4-溴-2,4,6-三氯-和2,4,6-三溴-4-甲基-环己-2,5-二烯酮)(4)和(5)分别提供相同的产品(3a),(6)和(7)用香叶基氰化物(1; R = CN)处理时。有证据表明二溴化物(3a)的形成可能是由于顺序反应。在十六烷基三甲基溴化铵的存在下,TBCO是在非常温和的条件下对多烯进行选择性溴化的极好试剂。