Allyl sulfoxides lithiated

Lithiated allyl sulfides (in common with allyl sulfoxides and selenides, but in contrast with allyl ethers and allyl amine derivatives) tend to react with alkyl halides at the a position, adjacent to S.1 The best a-selectivities are obtained with lithium-coordinating S-substituents such as pyridyl (114),85 imidazolyl (115), and dimethylaminocarbonyl (116).1... 

The 1,4-addition reaction of stabilized allylic carbanions with conjugated enones is normally complicated by the ambident reactivity of the carbanion. Clean 7-selective conjugate addition to cyclic enones, however, has been observed with lithiated allylic sulfoxides, phosphine oxides and phosphonates... 

The results of reactions of a-methyl chiral aldehydes and a lithiated allyl sulfoxide can be intrepreted in an analogous manner R. Annunziata, M. Cinquini, F. Cozzi, L. Raimondi and S. Stefanelli, Tetrahedron, 1986, 42, 5443. 

Although allylic sulfoxides produce allyl anions like (63) upon treatment with bases, 1-alkenyl sulfoxides afford a-lithiated derivatives with LDA (Scheme 39). /VA -Dimethyl-3-(phenylthio)-2-propenyl-amine also undergoes lithiation at the sp carbon next to sulfur. 

Allylic sulfoxides and sulfones are completely metallated in liquid ammonia by all alkali amides [1]. For metallation in organic solvents, LDA and BuLi are usually applied. The lithiation of allyltrimethylsilane can be conveniently achieved with BuLi TMEDA (or HMPT) or f-BuLi TMEDA (or HMPT) in THF-alkane mixtures [3], As in the case of the sulfur compounds, extension of the unsaturated system leads to an increased acidity. Thus H2C=CHCH=CHCH2SiMe3 can be metallated with the less strongly basic LDA in THF [4], For the metallation of allylic selenides, LDA seems to be the reagent of choice. Butyllithium will presumably attack on selenium. 

Lithiated allylic sulfoxides may be a-alkylated and the resulting products subjected to [2,3]-sigmatropic rearrangement induced by a thiophile to give allylic alcohols (eq 43). In contrast, alkenyl aryl sulfoxides produce a-lithiated species which are alkylated with Mel or PhCHO in good yields (eq 44). LDA has also been used to metalate allylic and propargylic selenides as weU as aryl vinyl selenides. ... 

In contrast to allylic phosphine oxides, phosphonates, sulfones and sulfoxides, the chemistry of lithiated allylic sulfoximines has been less extensively developed25 27. The reaction of lithiated racemic A-phenyl-A -(4-rnethylphenyl)-S -(2-propenyl)sulfoximine with either 2-cy-clopentenone or 2-cyclohexenone gave a complicated mixture with 1,4-oc-ad ducts being slightly favored over the 1,4-7-adducts. The yields of these adducts were poor25. In contrast, lithiated racemic Ar-tert-butyldiphenylsilyl-5-phenyl-5,-(2-propenyl)sulfoximine gives mainly 1,4-y-ad-ducts on reaction with the same enones26. 

In preliminary reports, the y-carbon of the carbanion of allyl phenyl sulfoxide has been shown to attack cyclopentenone and cyclohexenone by 1,4-addition to deliver vinyl sulfoxides. " The lithiated carbanion (75) of l-(phenylsulfinyl)-2-octene ( Z = 85 15) adds to 4-(-butoxycyclopent-2-en-l-one (74) to give jy -( )-vinylic sulfoxide (76) and anti-( )-vinylic sulfoxide (77) in the ratio of 79 21. It has been suggested that (76) arises almost exclusively from the ( )-(75), and (77) derives from the (Z)-(75). Both the products have the same geometry about the double bond, but differ in configuration at the allyiic carbon atom (equation 21), ... 

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