Asymmetric synthesis Andersen method

The purpose of this article is to present recent developments in the preparation of optically pure sulfoxides using both methods, mainly from 1990 to the present. Emphasis has been given to the bibliographic impact of each method. An application section is included after each route, especially in the case of variation in the Andersen methodology, where important advances have been achieved. It is not the aim of this article to review the chemistry of chiral sulfoxides—several excellent review articles have appeared on this subject, from the seminal review by Solladie19 in 1981 to other recent reviews.20 The literature has been surveyed up to January 1999. The preparation and utilization of chiral sulfoxides in asymmetric synthesis have been the subject of valuable comprehensive as well as specialized accounts which should be consulted for details and considered as complementary to this article. 

The use of sulfoxides as chiral synthons has, over recent years, become a highly dependable protocol in synthetic organic chemistry. To some extent, however, the use of sulfoxides in asymmetric synthesis has been limited by the lack of a reliable and general method for their preparation in optically pure form. In this review we present the development of chiral sulfoxide synthesis via nucleophilic displacement at sulfur from the pioneering work of Andersen in 1962 to more recent methods. Sulfoxides have become associated with many diverse areas of synthetic chemistry indeed, their ability to act as a handle for the stereoselective generation of chirality at proximate centres has attracted much research worldwide. 

There are several efficient methods available for the synthesis of homochiral sulfoxides [3], such as asymmetric oxidation, optical resolution (chemical or bio-catalytic) and nucleophilic substitution on chiral sulfinates (the Andersen synthesis). The asymmetric oxidation process, in particular, has received much attention recently. The first practical example of asymmetric oxidation based on a modified Sharpless epoxidation reagent was first reported by Kagan [4] and Modena [5] independently. With further improvement on the oxidant and the chiral ligand, chiral sulfoxides of >95% ee can be routinely prepared by these asymmetric oxidation methods. Nonetheless, of these methods, the Andersen synthesis [6] is still one of the most widely used and reliable synthetic route to homochiral sulfoxides. Clean inversion takes place at the stereogenic sulfur center of the sulfinate in the Andersen synthesis. Therefore, the key advantage of the Andersen approach is that the absolute configuration of the resulting sulfoxide is well defined provided the absolute stereochemistry of the sulfinate is known. 

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