Convenient and inexpensive procedure for oxidation of secondary alcohols to ketones
Convenient and inexpensive procedure for oxidation of secondary alcohols to ketones
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DOI：
10.1021/jo01298a066
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发表时间：
1980-05
影响因子：
3.6
通讯作者：
R. V. Stevens;K. Chapman;H. Weller
中科院分区：
文献类型：
--
作者：
R. V. Stevens;K. Chapman;H. Weller
醚在5当量的18-冠-6存在下变得对称。在不存在和存在5当量的18冠-6的情况下，1和2的阴离子的化学位移数据的比较揭示了1的257 Hz和2的144 Hz的变化。当抗衡离子是六氟磷酸盐时，观察到的2的较小化学位移变化再次与较低程度的离子配对一致。这一论点的核心是冠醚-重氮盐络合物5的形成是由于芳烃重氮阳离子的颈插入冠醚-重氮盐络合物5中。这种排列的证据包括在溶剂化、滴定和热分析中取代基的空间效应以及某些大环聚醚在芳烃重氮盐存在下的~ 1H NMR谱的变化。由于未络合的2的溶解度不足，因此不可能探测在添加18-冠-6时1和2在172-二氯乙烷中的1H NMR谱的变化。尽管1和2的叔丁基氢和3，5芳环氢的化学位移不受18-冠-6的存在的影响，但在18-冠-6的存在下，2，6芳环氢向高场移动7- 8Hz。仅邻位氢的化学位移变化为所提出的重氮离子-冠醚络合物5提供了进一步的证据。
ether became symnietrical in the presence of 5 equiv of 18-crown-6. Comparison of the chemical shift data for the anions of 1 and 2 in the absence and presence of 5 equiv of 18crown-6 reveals a change of 257 Hz for 1 and 144 Hz for 2. The smaller chemical shift change observed for 2 is again consistent with a lesser degree of ion pairing when the counterion is hexafluorophosphate. Central to this argument is the formulation of the crown ether-diazonium salt complex 5 as resulting from insertion of the neck of the arenediazonium cation into a crown ether ~ o l l a r . ~ J ~ J ~ PrevioiJs evidence for this arrangement includes steric effects of substituents in sol~bilization~~'~ and titration cal~rimetric '~ studies and 'H NMR spectral changes of certain macrocyclic polyethers in the presence of arenediazonium salt^.^,'^ Because of insufficient solubility of uncomplexed 2 it was not possible to probe for changes in the 'H NMR spectra of 1 and 2 in 172-dichloroethane upon addition of 18-crown-6. However, such measurements could be made in dimethyl sulfoxide and are summarized in Table V. Although the chemical shifts of the tert-butyl group hydrogens and the 3,5 aromatic ring hydrogens of 1 and 2 are unaffected by the presence of 18-crown-6, the 2,6 aromatic ring hydrogens are shifted upfield by 7-8 Hz in the presence of 18-crown-6. This chemical shift change for only the ortho hydrogens provides further evidence for the proposed diazonium ion-crown ether complex 5.