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首页> 外文期刊>Chemistry: A European journal >Mechanistic studies on a sulfoxide transfer reaction mediated by diphenyl sulfoxide/triflic anhydride
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Mechanistic studies on a sulfoxide transfer reaction mediated by diphenyl sulfoxide/triflic anhydride

机译：二苯基亚砜/三氟甲磺酸酐介导的亚砜转移反应的机理研究

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摘要

Sulfoxides are frequently used in organic synthesis as chiral auxiliaries and reagents to mediate a wide variety of chemical transformations. For example, diphenyl sulfoxide and triflic anhydride can be used to activate a wide range of glycosyl donors including hemiacetals, glycals and thioglycosides. In this way, an alcohol, enol or sulfide is converted into a good leaving group for subsequent reaction with an acceptor alcohol. However, reaction of diphenyl sulfoxide and triflic anhydride with oxathiane-based thioglycosides, and other oxathianes, leads to a different process in which the thioglycoside is oxidised to a sulfoxide. This unexpected oxidation reaction is very stereoselective and proceeds under anhydrous conditions in which the diphenyl sulfoxide acts both as oxidant and as the source of the oxygen atom. Isotopic labelling experiments support a reaction mechanism that involves the formation of oxodisulfonium (S-O-S) dication intermediates. These intermediates undergo oxygen-exchange reactions with other sulfoxides and also allow interconversion of axial and equatorial sulfoxides in oxathiane rings. The reversibility of the oxygen-exchange reaction suggests that the stereochemical outcome of the oxidation reaction may be under thermodynamic control, which potentially presents a novel strategy for the stereoselective synthesis of sulfoxides. Sending out an SOS: The diphenyl sulfoxide/triflic anhydride combination is widely used as an activating agent for glycosylation reactions. However, oxathiane glycosyl donors are instead oxidised to sulfoxides in a stereoselective and reversible reaction. NMR spectroscopy and isotopic labelling experiments reveal the presence of oxodisulfonium (S-O-S) dication intermediates that can undergo oxygen exchange with other sulfoxides (see scheme).
机译：亚砜经常在有机合成中用作手性助剂和试剂，以介导多种化学转化。例如，二苯基亚砜和三氟甲磺酸酐可用于活化各种糖基供体，包括半缩醛，糖基和硫代糖苷。以这种方式，将醇，烯醇或硫化物转化为良好的离去基团，用于随后与受体醇反应。然而，二苯基亚砜和三氟甲磺酸酐与基于氧杂蒽基的硫代糖苷和其他氧杂蒽基的反应导致了不同的过程，其中硫代糖苷被氧化为亚砜。这种出乎意料的氧化反应是非常立体选择性的，并且在无水条件下进行，在该条件下二苯亚砜既起氧化剂的作用，又起氧原子的来源的作用。同位素标记实验支持涉及氧二s（S-O-S）指示中间体形成的反应机理。这些中间体与其他亚砜进行氧交换反应，并且还允许氧杂蒽环中的轴向和赤道亚砜相互转化。氧交换反应的可逆性表明，氧化反应的立体化学结果可能处于热力学控制下，这可能为亚砜的立体选择性合成提供了一种新的策略。发出SOS：二苯亚砜/三氟甲磺酸酐的组合被广泛用作糖基化反应的活化剂。但是，在立体选择性和可逆反应中，氧杂蒽基糖基供体被氧化成亚砜。 NMR光谱和同位素标记实验揭示了氧二odi（S-O-S）指示中间体的存在，该中间体可与其他亚砜进行氧交换（请参阅方案）。

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