Chiral sulfoxides: advances in asymmetric synthesis and problems with the accurate determination of the stereochemical outcome

Abstract

Chiral sulfoxides are in extremely high demand in nearly every sector of the chemical industry concerned with the design and development of new synthetic reagents, drugs, and functional materials. The primary objective of this review is to update readers on the latest developments from the past five years (2011-2016) in the preparation of optically active sulfoxides. Methodologies covered include catalytic asymmetric sulfoxidation using either chemical, enzymatic, or hybrid biocatalytic means; kinetic resolution involving oxidation to sulfones, reduction to sulfides, modification of side chains, and imidation to sulfoximines; as well as various other methods including nucleophilic displacement at the sulfur atom for the desymmetrization of achiral sulfoxides, enantioselective recognition and separation based on either metal-organic frameworks (MOF's) or host-guest chemistry, and the Horner-Wadsworth-Emmons reaction. A second goal of this work concerns a critical discussion of the problem of the accurate determination of the stereochemical outcome of a reaction due to the self-disproportionation of enantiomers (SDE) phenomenon, particularly as it relates to chiral sulfoxides. The SDE is a little-appreciated phenomenon that can readily and spontaneously occur for scalemic samples when subjected to practically any physicochemical process. It has now been unequivocally demonstrated that ignorance in the SDE phenomenon inevitably leads to erroneous interpretation of the stereochemical outcome of catalytic enantioselective reactions, in particular, for the synthesis of chiral sulfoxides. It is hoped that this two-pronged approach to covering the chemistry of chiral sulfoxides will be appealing, engaging, and motivating for current research-active authors to respond to in their future publications in this exciting area of current research.

Imine‐Based Covalent Organic Frameworks as Photocatalysts for Metal Free Oxidation Processes under Visible Light Conditions

“…[1] In fact, at present, it is used for the preparation of relevant compounds such as epoxides (epoxidation) [2] and acetaldehyde (Wacker process) [3] from double bonds, ketones from alcohols [1] and sulfoxides from thioethers, [4] among other important oxidations. [1] In fact, at present, it is used for the preparation of relevant compounds such as epoxides (epoxidation) [2] and acetaldehyde (Wacker process) [3] from double bonds, ketones from alcohols [1] and sulfoxides from thioethers, [4] among other important oxidations.…”

“…Oxidation reactions are one of the most important transformations in society and at an industrial level. [1] In fact, at present, it is used for the preparation of relevant compounds such as epoxides (epoxidation) [2] and acetaldehyde (Wacker process) [3] from double bonds, ketones from alcohols [1] and sulfoxides from thioethers, [4] among other important oxidations. These reactions are considered fundamental in organic synthesis since they allow the addition of new functional groups but frequently are accompanied by other secondary reactions, generally exhibiting low regioselectivities and poor chemoselectivities.…”

Optically Active Selenoxides: Structural and Synthetic Aspects

“…The purpose of this mini review is to provide available information on both topics in order to stimulate additional research in this field. The rationale for this research topic is the structural similarity between selenoxides and sulfoxides, which play a very important role as new synthetic reagents, biologically active compounds and new functional materials [71]. Therefore, it is reasonable to expect that optically active selenoxides should be just as useful as sulfoxides when they have sufficiently high optical stability.…”

Biotechnological Methods of Sulfoxidation: Yesterday, Today, Tomorrow

“…These enzymes are involved in the aerobic degradation of aromatic compounds and they are mainly catalyzed for the cleavage of aromatic ring and the cis-dihydroxylation of arenes. [52] 3.3.1. Toluene Dioxygenase Toluene dioxygenase (TDO, EC 1.14.12.11) from Pseudomonas putida F1 was able to oxidise thioanisole mainly to the (R)-sulfoxide (ee > 98%) [53,54].…”

“…These compounds can be found in the environment, e.g., from petroleum, coal, and products of its combustion. In the case of sulfoxidation by TDO in addition to the formation of the desired sulfoxides, the formation of a variety of other products has been also observed, e.g., the formation of di-and monohydroxyls or dimers [52,55]. The optimal use of chloroperoxidase from C. fumago in sulfoxidation depends on the method of adding an oxidizer such as hydrogen peroxide.…”