1,4-DIOXASPIRO[2.2]PENTANES - SYNTHESIS, SPECTROSCOPIC PROPERTIES, AND REACTIONS WITH NUCLEOPHILES
1,4-DIOXASPIRO[2.2]PENTANES - SYNTHESIS, SPECTROSCOPIC PROPERTIES, AND REACTIONS WITH NUCLEOPHILES
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DOI：
10.1021/jo00003a044
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发表时间：
1991-02-01
影响因子：
3.6
通讯作者：
LIN, F
中科院分区：
文献类型：
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作者：
CRANDALL, JK;BATAL, DJ;LIN, F
一些简单的联烯被二甲基二氧杂环烷氧化，以较高的产率清洁地转化为相应的1，4-二氧杂螺[2.2]戊烷。单取代和三取代联烯使反对映异构体具有良好的立体选择性，而1，3-二取代联烯只对反、反异构体有轻微的偏好，除非空间效应非常严重。立体化学指定是基于空间构型的考虑和一组允许结构归属的一致的核磁共振特征。在缓冲条件下，一系列亲核试剂(水、醇、胺、苯硫酚、醋酸酯、氯化物和氟化物)与这些中间体的加成反应顺利进行，得到了一般类型的高官能化产物5。这些反应对S(N)2取代反应具有适当的选择性，在可观察到这些特征的情况下，即对取代较少的环氧化物碳的区域选择性攻击和取代部位的构型反转。在酸性条件下，二氧杂五环戊烷产生其他类型的产物的混合物，这些产物似乎来自碳阳离子过程。
A number of simple allenes have been converted cleanly to the corresponding 1,4-dioxaspiro[2.2]pentanes in good yields by oxidation with dimethyldioxirane. Mono- and trisubstituted allenes give the anti diastereomers with good stereoselectivity, whereas 1,3-disubstituted allenes show only a slight preference for the anti,anti isomers, unless steric effects are extreme. Stereochemical assignments are based on steric considerations and a consistent set of NMR characteristics that permit structural attributions. The addition of a range of nucleophiles (water, alcohols, amines, thiophenol, acetate, chloride, and fluoride) to these intermediates proceeded smoothly under buffered conditions to give highly functionalized products of general type 5. These reactions were shown to take place with the appropriate selectivities for S(N)2 substitutions in instances where these features were observable, namely, regioselective attack at the less-substituted epoxide carbon and inversion of configuration at the site of substitution. Under acidic conditions dioxaspiropentanes gave mixtures of other types of products, which appear to arise from carbocationic processes.