Sulfoximines cyclopropanes

Another example of the superiority of the alkoxy group as a directing group was reported by Johnson in his synthesis of enantiomericaUy pure cyclopropyl ketones after auxiliary cleavage (equation 56). In that case, the product resulting from a sulfoximine directed cyclopropanation was never observed. 

Simmons-Smith cyclopropanation of -hydroxysulfoximines (equation 74) . However, access to the pure bicyclo[3.1.0] derivative required chromatographic separation of the diastereomeric sulfoximine adducts. 

Syntheses of cyclopropanes and oxiranes of high optical activity could be achieved [480] through reactions of anions derived from optically active sulfoximines or sulfoxides, respectively, with Michael acceptors or aldehydes, separation of the diastereoisomeric adducts and conversion of these to the cyclized products. 

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-... 

Stabilized lithiated sulfoximines (112) undergo highly diastereoselective Michael additions to cyclic enones at —78 °C under kmetically controlled conditions. At room temperature, the initially formed adducts (113) undergo intramolecular substitution of the sulfonimidoyl group, with inversion of configuration to afford the corresponding cyclopropanes (114).92... 

Resolved P-hydroxy sulfoximines derived from cyclic enones undergo dias-tereoselective Simmons-Smith cyclopropanation reactions to give, after thermolysis, cyclopropylketones in high enantiomeric purity (94-98%). Cyclopropanation occurs syn to the hydroxyl group of the P-hydroxy sulfoximine. This method is less diastereoselective for acyclic enones.73... 

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. ... 

Besides serving as a useful tool for resolution, the sulfoximine addition adduct can be utilized to direct such reactions as the Simmons-Smith cyclopropanation and 0s04 addition to an alkene. ... 

A combination of resolution and diastereofacial cyclopropanation has been used to prepare a variety of cyclopropyl ketones with high optical purity77. Optically active lithiated (S)-N,S-dimethyl-S-phenylsulfoximine (17) is added to prostereogenic enones such as 16, and the resulting diastereomeric allylic alcohols 18 are separated by column chromatography. Hydroxyl-directed Simmons-Smith cyclopropanation (see Section 1.6.1.5.1.2.) provides intermediates which are thermally decomposed to release the optically pure cyclopropyl ketones 20 and the sulfoximine 19. 

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. 

Phosphorus- or sulfur-ylids are frequently used in pyrethroid chemistry. 5-Methylsorbinic ester 19 is readily cyclopropanated by the unfortunately not so easy to prepare diphenylisopropylidene sulfuran 20 [30-32] (Reaction schemes 11 and 12). Similarly, phenyl-isopropyl-sulfoximine anion 21 is also suitable as a isopro-pylidene source. 

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