Sulfoximine ylides

The synthetic utility of a-phosphorus- and a-thio-stabilized carbanions is the subject of numerous reviews.21 Notable are additions of phosphonium ylides (237),183 sulfonium ylides (238),l84 ° oxosulfo-nium ylides (239)184 " and sulfoximine ylides (240)184,1 to electron-deficient alkenes which afford nucleophilic cyclopropanation products. In contrast, with a-(phenylthio)-stabilized carbanions, which are not acyl anion equivalents, either nucleophilic cyclopropanation or retention of the hetero substituent occurs, depending on the acceptor and reaction conditions used. For example, carbanion (241) adds to 1,1-... 

The few published attempts at the asymmetric epoxidation of carbonyl compounds with chiral sulfur ylides have been reviewed. Thus far, such processes have not been very useful synthetically. For example, reaction of benzaldehyde with an optically pure sulfoximine ylide only afforded an qioxide in 20% enantiomeric excess. More recently, chiral sulfur methylides have provided tra/i -stilbene oxides in up to 83% ee An example of optical induction observed in reactions t ng place with a chiral phase transfer reagent was reported, but later disputed. ... 

Oxidative cleavage of oxosulfonium ylides as well as of sulfoximines leads to sulfone formation. In the course of oxidations of dialkoxy sulfuranes(IV) by hydrogen peroxide" or t-butyl hydroperoxide , sulfone formation takes place (equation 99). 

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 methylation of sulfoximines 45 with Me30BF4 proceeded readily and gave the corresponding cyclic aminosulfoxonium salts 46 in quantitative yields. Upon treatment with LiN(H)t-Bu first at-78 °C and then at room temperature, salts 46 delivered the enantio- and diastereomerically pure bicyclic 2,3-dihydrofurans 50 cleanly in high overall yields. It is proposed that the reactions of the aminosulfoxonium salts 40 and 46 with the lithium amide at low temperatures afford the vinyl aminosulfoxonium ylides 41 and 47, respectively. These alkylidene carbenoids eliminate sulfinamide 35 at higher temperatures with formation of the alkylidene carbenes 42 and 48, respectively. Subsequently, the alkylidene... 

Chiral alkenyl and cycloalkenyl oxiranes are valuable intermediates in organic synthesis [38]. Their asymmetric synthesis has been accomplished by several methods, including the epoxidation of allyl alcohols in combination with an oxidation and olefination [39a], the epoxidation of dienes [39b,c], the chloroallylation of aldehydes in combination with a 1,2-elimination [39f-h], and the reaction of S-ylides with aldehydes [39i]. Although these methods are efficient for the synthesis of alkenyl oxiranes, they are not well suited for cycloalkenyl oxiranes of the 56 type (Scheme 1.3.21). Therefore we had developed an interest in the asymmetric synthesis of the cycloalkenyl oxiranes 56 from the sulfonimidoyl-substituted homoallyl alcohols 7. It was speculated that the allylic sulfoximine group of 7 could be stereoselectively replaced by a Cl atom with formation of corresponding chlorohydrins 55 which upon base treatment should give the cycloalkenyl oxiranes 56. The feasibility of a Cl substitution of the sulfoximine group had been shown previously in the case of S-alkyl sulfoximines [40]. 

Ylides derived from the salts obtained by A. A -dialkylation of sulfoximines and anions derived from A -tosylsulfoximines are useful reagents for the synthesis of epoxides or cyclopropanes from aldehydes and ketones or enones. ... 

The most commonly used reagents to effect the addition of a methylene group to an aldehyde or ketone are sulfur ylides such as dimethylsulfonium methylide (1) or dimethyloxosulfonium methylide (2) (Corey-Chaykovsky reaction). This reaction is well reviewed in standard treatises of organic synthesis - and several useful monographs. - This update will concentrate on progress attained from 1975. The reader is also encouraged to consult reviews on the chemistry of the related sulfoximine-derived ylides such as (3). -"... 

N-Tosylsulfoximines and sulfilimines have successfully been used as sulfur ylide precursors in oxirane synthesis <85MI 103-02,85PS(24)53i, 92SR57). Using a chiral sulfoximine (S-neomenthyl-Af-tosyl oxosulfonium methylide), various aromatic aldehydes and ketones have been converted to oxiranes in relatively high enantiomeric excess (56-86% ee) (94TA1513). 

For the synthesis of cyclopropyl amino acids, Williams has used an oxazinone auxiliary (cf. Scheme 3.12) as an electrophilic component in a sulfur ylide cyclopropanation using Johnson s sulfoximines, as illustrated in Scheme 6.41 [148]. Surprisingly, the sulfur ylide approaches from the P face the authors speculate that there may be some sort of 7t-stacking between the phenyls on the oxazinone ring and the phenyl in the sulfoximine to account for this [149]. With Corey s [147] dimethylsulfonium methylide, the diastereoselectivity was only about 75%, but with Johnson s sulfoximines (used in racemic form), only one diastereomer could be detected for most substrates studied (with the exception of R = H, [149]). Dissolving metal reduction afforded moderate yields of the cyclopropyl amino acids. 

Extension of the synthetic versatility of sulfur ylides so that substituted methylene groups, as well as methylene itself, can be transferred has been accomplished by modification of the sulfur substituents. Entry 6 in Scheme 2.9 illustrates a transfer of an isopropylidene unit. Even greater structural flexibility has been achieved by use of nucleophiles derived from sulfoximines." The N-p-toluenesulfinyl sulfoximines appear to be particularly promising reagents. They are prepared from sulfoxides by reaction with p-toluenesulfonyl azide. Strong base... 

Nitrogen Atom Transfer to Heteroatoms. PhI=NTs reacts with heteroatom lone pairs to generate ylides. Reaction with triphenylphosphine at 100 °C affords 69% of the phosphinimine (1) (eq 3). Likewise, PhI=NTs reacts with thioanisole to generate the iminosulfurane (2) in 49% yield (eq 4) and with dimethyl sulfoxide to quantitatively produce the sulfoximine (3) (eq 5). 

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