Chiral sulfur reagents

Mikolajczyk, M. Drabowicz, J. Kielbasihski, P. Chiral Sulfur Reagents, CRC Press, Boca Raton, 1997. 

M. Mikolajezk, J. Drabowicz and P. Kielbasinski, in Chiral Sulfur Reagents, CRC Press, USA, 1997. 

In recent years three other examples of asymmetric induction have been described in the literature in which the chiral sulfur reagent that induces optical activity is converted into another chiral sulfur compound. The first reaction of this type is the chlorination of 2,2-diphenylaziridine (265) by means of the optically active A -chloro-phenylmethylsulfoximide (266), affording optically active A -chloro-2, 2-diphenylaziridine (267) and the unsubstituted sulfoximide 149 (197). In this case asymmetric induction is observed on the nitrogen atom. 

A few vinylzinc reagents have been added to aldehydes in the presence of chiral sulfur-containing ligands. As an example, Seto et al. reported, in 2005, the synthesis of dipeptide A-acylethylenediamine-based ligands by parallel... 

However, the major factor stimulating the rapid development of static and dynamic sulfur stereochemistry was the interest in the mechanism and steric course of nucleophilic substitution reactions at chiral sulfur. Very recently, chiral organic sulfur compounds have attracted much attention as useful and efficient reagents in asymmetric synthesis. 

C. Reactions of Chiral Sulfur Compounds with Electrophilic Reagents... 

As the last point in Sect. IV, we discuss briefly the reactions of chiral sulfur compounds with electrophilic reagents. In contrast to nucleophilic substitution reactions, the number of known electrophilic reactions at sulfur is very small and practically limited to chiral tricoordinate sulfur compounds that on reacting with electrophilic reagents produce more stable tetracoordinate derivatives. It is generally assumed that the electrophilic attack is directed on the lone electron pair on sulfur and that the reaction is accompanied by retention of configuration. As typical examples of electrophilic reactions at tricoordinate sulfur, we mention oxidation, imination, alkylation, and halogenation. All these reactions were touched on in the section dealing with the synthesis of chiral tetracoordinate sulfur compounds. 

The cis- and frans-sulfoxides (551) and (552) have been O-methylated with Meerwein s reagent. Reaction of the methoxy derivative with MeMgBr proceeds with inversion of configuration (Scheme 211) (74JA8026). The stereochemical course of the interconversions of sulfoxide, sulfimide and sulfoximide in the 2,3-dihydrobenzo[6]thiophene series has been investigated (73JA1916). The reaction cycle (Scheme 212) involves both nucleophilic and electrophilic substitution at chiral sulfur. Inversion of configuration takes place in the conversion of (553) to (554) in pyridine. 

A recent report details absolute stereochemical control at levels of up to 75 25 in ene reactions, although typical levels are lower35. This selenium reagent has two identical, chiral sulfur atoms and it is these stereogenic centers that provide for reagent-based control of absolute stereochemistry. 

The chiral sulfur(vi) reagent, A -[[J-(/i-toluenesulfonimido)-6 -(/i-tolyl)]sulfonyl]amide 431 upon reaction with iodosylbenzene 426 affords in situ the chiral iminoiodane 432. In the presence of Cu(MeCN)4PF6 as catalyst, iminoiodane 432 forms the complex 433 that very efficiently transfers the nitrene moiety together with the stereogenic information under stoichiometric conditions to a variety of alkenes 414 the corresponding aziridines 434 were obtained with diastereoselectivities up to 60% (Scheme 112) <20040L4503>. 

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