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螺旋手性氧离子中立体氧的控制
作者:小柯机器人 发布时间:2023/3/19 22:54:47


英国牛津大学Smith, Martin D.团队报道了螺旋手性氧离子中立体氧的控制。相关研究成果发表在2023年3月15日出版的《自然》。

四面体碳立体中心的控制仍然是现代合成化学的重点,并且是由它们的构型稳定性实现的。相比之下,三取代的氮、磷和硫化合物发生金字塔反转是一种被广泛利用的、基本的且公认的立体化学现象。然而,在带正电的氧原子上带有三个取代基的氧鎓离子化合物的立体化学发展很差,并且除了作为活性中间体存在之外,氧鎓在合成中的应用很少。没有构型稳定的氧鎓离子的例子,其中氧原子是唯一的立体发生中心,这可能是由于对氧金字塔反转的低势垒以及认为所有氧鎓阳离子都是高度反应性的。

该文中,研究人员描述了一种螺旋手性三芳基氧鎓离子的设计、合成和表征方法,其中通过几何限制阻止了氧孤对的反转,使其能够作为构型的决定因素。合成和量子计算相结合的方法描述了能够产生构型稳定和室温可隔离的盐的设计原理。研究表明,反演的势垒大于110kJmol-1,并概述了转换的过程。

该研究是手性非外消旋和构型稳定分子的唯一例子,其中氧原子是唯一的立体中心。

附:英文原文

Title: Control of stereogenic oxygen in a helically chiral oxonium ion

Author: Smith, Owen, Popescu, Mihai V., Hindson, Madeleine J., Paton, Robert S., Burton, Jonathan W., Smith, Martin D.

Issue&Volume: 2023-03-15

Abstract: The control of tetrahedral carbon stereocentres remains a focus of modern synthetic chemistry and is enabled by their configurational stability. By contrast, trisubstituted nitrogen1, phosphorus2 and sulfur compounds3 undergo pyramidal inversion, a fundamental and well-recognized stereochemical phenomenon that is widely exploited4. However, the stereochemistry of oxonium ions—compounds bearing three substituents on a positively charged oxygen atom—is poorly developed and there are few applications of oxonium ions in synthesis beyond their existence as reactive intermediates5,6. There are no examples of configurationally stable oxonium ions in which the oxygen atom is the sole stereogenic centre, probably owing to the low barrier to oxygen pyramidal inversion7 and the perception that all oxonium ions are highly reactive. Here we describe the design, synthesis and characterization of a helically chiral triaryloxonium ion in which inversion of the oxygen lone pair is prevented through geometric restriction to enable it to function as a determinant of configuration. A combined synthesis and quantum calculation approach delineates design principles that enable configurationally stable and room-temperature isolable salts to be generated. We show that the barrier to inversion is greater than 110kJmol1 and outline processes for resolution. This constitutes, to our knowledge, the only example of a chiral non-racemic and configurationally stable molecule in which the oxygen atom is the sole stereogenic centre.

DOI: 10.1038/s41586-023-05719-z

Source: https://www.nature.com/articles/s41586-023-05719-z

期刊信息
Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:69.504
官方网址:http://www.nature.com/