From carbohydrates to the discovery of prounced heteroatomic effects on anionically accelerated [3,3]-sigmatropic rearrangements
學年 88
學期 2
出版（發表）日期 2000-06-01
作品名稱 From carbohydrates to the discovery of prounced heteroatomic effects on anionically accelerated [3,3]-sigmatropic rearrangements
作品名稱（其他語言）
著者 Paquette, L.A.
單位 淡江大學化學學系
出版者
著錄名稱、卷期、頁數 European journal of organic chemistry 2000(12), pp.2187-2194
摘要 The (Z)-(iodovinyl)oxetane 12 was prepared from D-glucose and the acyclic analog 18 was obtained from D-mannitol. Following the generation of their lithium derivatives by halogen−metal exchange, coupling to the enantiopure vinyl-substituted norbornanones 20, 23, and 29 proceeded exclusively via endo attack to deliver the targeted exo-carbinols. The anionic oxy-Cope rearrangements of 21 and 24 were seen to differ appreciably in rate. While the sulfur derivative 24 experiences [3,3] sigmatropy with a half-life of less than a minute at −78 °C, its oxygen analogue 21 proved unreactive below −20 °C under entirely comparable conditions. This phenomenon is critically examined in a synthetic context involving 26 and 30, where the heavily functionalized acyclic side chain involved previously is supplanted by an oxetane assembly. In the sulfur example, isomerization occurs very rapidly as before with 100% transfer of chirality. The kinetic response of vinyl ether 26 now proved to be entirely comparable. However, the pathway followed in this instance was intramolecular nucleophilic attack by the “naked” alkoxide at the less substituted C−O bond of the oxetane with ring cleavage and formation of alcohol 28. The global findings provide a glimpse of the subtle way in which [3,3]-sigmatropic transpositions can be modulated by heteroatomic substitution.
關鍵字
語言 en
ISSN 1434-193X 1099-0690
期刊性質 國外
收錄於
產學合作
通訊作者
審稿制度 否
國別 DEU
公開徵稿
出版型式 ,電子版,紙本
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