Use of Sulfoximines

Unfortunately, reductive elimination of diastereoisomerically pure )S-hydroxy-sulfoximines leads to mixtures of ( )- and (Z)-alkenes (Table 3.16) [152]. In general, the elimination of sulfoximines is less trans-selective [3,152]. 

As can be seen from this chapter, the Julia reaction is a powerful tool for the preparation of C-C double bonds. Mono-, 1,1-di- and ( )-l,2-disubstituted olefins 

Both sulfoxide- and sulfoximine-based modifications are promising alternatives for the synthesis of pure syn or anti coupling adducts and might lead to the stereocontrolled preparation of olefins. Moreover, great efforts are being made by several groups to enhance the stereoselectivity of the one-step procedures discussed in Section 3.5. It might soon be expected that any C-C double bond, no matter which isomer or how substituted it is, should be accessible by means of the Juha olefination reaction. 

Simpkins, in Sulfones in Organic Synthesis, Tetrahedron Organic Chemistry series 10 Pergamon Press, London, 1993. 

Pascali, a. Umani-Ronchi,/. Chem. Soc., Chem. Commun. 1973, 

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As an extension of these studies on the use of sulfoximines in asymmetric reductions, BlNOL-derived phosphino sulfoximines of the 105 type were tested in both rhodium-catalyzed hydrogenations (yielding optically active diesters 104 or amino acid derivatives Scheme 2.1.1.35) and palladium-catalyzed allylic alkylations (not shown) in collaboration with Reetz and Gais [81, 82]. Here, enantioselectivities of up to >99 and 66% ee, respectively, were achieved. 

The use of sulfoximines in the syntheses of optically active compounds has been reported [429]. A remarkable ketone methylcnation with optical resolution was realized. A highly selective diastereofacial addition of an enantiopure sulfoximine to a racemic ketone, chromatographic separation of the two diastereoisomers and reductive cleavage yielded both enantiomers of p-panasinsene [430], isolated from the root of ginseng, a herb used in Chinese folk medicine. 

Bolm et al. [106] have carefully studied the synthesis and the hganding ability of salen-like bis(sulfoximines). The chirahty which is indeed generally introduced via the use of chiral diamines in the salen series, is in sulfoximines present via the sulfur atom. They investigated the Diels-Alder cycloaddition between cyclopentadiene and acryloyl-2-oxazolidinones with various bis(sulfoximines) (see Scheme 42) and Cu(OTf)2 as the copper source [107]. 

On the other hand, Bolm et al. have reported, more recently, the use of BINOL-derived A -phosphino sulfoximines as ligands in the rhodium-catalysed hydrogenation of dimethyl itaconate and a-acetamidoacrylates, achieving excellent enantioselectivities of up to 99% ee (Scheme 8.12). In the main... 

In order to avoid the use of a rather expensive and potentially dangerous borane complex, Bolm et al. have developed an improved procedure for the borane reduction of ketones, which involved two inexpensive reagents namely NaBH4 and TMSCI. The reduction of a series of ketones was examined applying these novel reaction conditions and the same p-hydroxy sulfoximine ligand to that described above (Scheme 10.56). For most ketones, both the level of asymmetric induction and the yield compared favorably to the precedent results. 

Aside from the methylide and cyclopropylide reagents, the sulfonium ylides are not very stable. A related group of reagents derived from sulfoximines offers greater versatility in alkylidene transfer reactions.286 The preparation and use of this class of ylides is illustrated below. 

The Harmata group has also developed a route to enantiomerically pure 2,1-benzothiazines. The process involves the /V-arylation of sulfoximines using the Buchwald-Hartwig reaction conditions, <02MI3 99JOM(576)125> a reaction first reported by Bolm... 

Gais and co-workers recently reported the preparation and use of chiral sulfoximine-substituted allyltitanium(iv) complexes of type 78 for the asymmetric synthesis of 3-substituted unsaturated proline derivatives 79 (Scheme 31).108... 

ASYMMETRIC REDUCTION OF CHLOROACETOPHENONE USING A SULFOXIMINE CATALYST S]... 

The first attempts to develop reactions offering control over the absolute stereochemistry of a chiral center, created by y-selective substitution of an achiral allylic alcohol-derived substrate, involved the use of chiral auxiliaries incorporated in the nucleofuge. The types of stereodirecting groups utilized vary, and have included sulfoximines [15], carbamates [16], and chiral heterocyclic sulfides [17-19]. 

During the investigation of the synthesis and use of sulfilimines (such as 22 and 23) [21, 23, 24] and sulfondiimides (of the 25 type) [27], it became apparent that appropriately substituted nonsymmetric derivatives of these compounds were much more difficult to prepare in enantiopure form than their sulfoximine counterparts. It was therefore decided to retain the sulfur/oxygen moiety and to concentrate further efforts exclusively on the synthesis and application of sulfoximines. 

The initial observation indicating that such C-arylation was indeed feasible stemmed from an attempted palladium-catalyzed double N-arylation reaction (for details of this type of coupling reaction, see below). With the objective of preparing C2-symmetric bissulfoximine 28, dibromonaphthalene 29 was treated with an excess of sulfoximine 9 under standard coupling conditions using [Pd2dba3]/ BINAP as a catalyst in the presence of a base and, to our surprise, cyclic sulf-oximine 30 was obtained in excellent yield (Scheme 2.1.1.8) [30]. 

Subsequently, alternative syntheses of sulfoximine-containing heterocycles were studied, and one such approach was based on Grubbs olefin metathesis reaction. Using the ruthenium carbene complex 39 as catalyst, a wide range of... 

Finally, we demonstrated that the N-arylation of sulfoximines could also be achieved using arylboronic acids as an aryl source [54]. This protocol (with the formally umgepolte reagents 65 Scheme 2.1.1.23) has the advantages that the... 

For the use of ZnEt2 as a base and structural studies of the resulting sulfoximine-containing zinc enolates, see C. Bolm,). Muller, M. Zehnder, M. A. Neuburger, Chem. Eur. J. 1995, 1, 312. 

The sulfoximine group has proved to be an excellent ortho-directing group in lithiation reactions.77 The use of prochiral electrophiles has afforded ortho-functionalized (g) arylsulfoximines in good yields and modest to good diastereoselectivities up to 95%. 

For the use of optically active P-hydroxy sulfoximines as ligands for enantioselective catalytic reactions, see Section VII. 

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