Carbanions allylic sulfinyl

This type of asymmetric conjugate addition of allylic sulfinyl carbanions to cyclopen-tenones has been applied successfully to total synthesis of some natural products. For example, enantiomerically pure (+ )-hirsutene (29) is prepared (via 28) using as a key step conjugate addition of an allylic sulfinyl carbanion to 2-methyl-2-cyclopentenone (equation 28)65, and (+ )-pentalene (31) is prepared using as a key step kinetically controlled conjugate addition of racemic crotyl sulfinyl carbanion to enantiomerically pure cyclopentenone 30 (equation 29) this kinetic resolution of the crotyl sulfoxide is followed by several chemical transformations leading to (+ )-pentalene (31)68. 

Pokin, A. A., Kushko, A. O., Kiri], A. V., Yurchenko, A. G., Schleyer, P. v. R. Direct Transformations of Ketones to y-Unsaturated Thiols via [2,3]-Sigmatropic Rearrangement of Allyl Sulfinyl Carbanions A Combined Experimental and Computational Study. J. Org. Chem. 2000,... 

S Addition of Allylic Sulfinyl Carbanions to 0-4) Bonds... 

Sulfoxides (R1—SO—R2), which are tricoordinate sulfur compounds, are chiral when R1 and R2 are different, and a-sulfmyl carbanions derived from optically active sulfoxides are known to retain the chirality. Therefore, these chiral carbanions usually give products which are rich in one diastereomer upon treatment with some prochiral reagents. Thus, optically active sulfoxides have been used as versatile reagents for asymmetric syntheses of many naturally occurring products116, since optically active a-sulfinyl carbanions can cause asymmetric induction in the C—C bond formation due to their close vicinity. In the following four subsections various reactions of a-sulfinyl carbanions are described (A) alkylation and acylation, (B) addition to unsaturated bonds such as C=0, C=N or C= N, (C) nucleophilic addition to a, /5-unsaturated sulfoxides, and (D) reactions of allylic sulfoxides. 

In contrast, few examples of conjugate additions of nonallylic a-sulfinyl (or a-sulfonyl) carbanions have been reported (for allylic oc-sulfinyl carbanion additions, see Section 1.2.2.5.1). Notable is the dia-stereoselective addition of alkyl f-butyl sulfoxides (245) to a,(3-unsaturated esters (equation 20)187 which is complementary to the diastereoselective addition of enolates to 3-substituted-a,f3-unsaturated sulfoxides (equation 20). 

A novel synthesis of allyl sulfoxides has been developed by the reaction of primary o -lithiosulfinyl carbanions with group 6 Fischer carbene complexes (Scheme 9).49 The Fischer carbene complex experiments involve a 1,2-addition of two molecules of sulfinyl carbanion to give an intermediate that, after a -elimination, furnishes the mentioned product. 

The reactions between a-metalloalkyl sulfoxides and electrophiles have been extensively studied. Although alkylations of the sodium or potassium salts of dialkyl sulfoxides are not always very efficient since a,a -dialkylated sulfoxides are often produced (or stilbene in the case of methyl-sulfinyl carbanion and benzyl bromide ), those employing the lithioalkyl aryl sulfoxides work more efficiently with alkyl or allyl halides " and with epoxides. " " Typical examples of these alkylations, allylations and hydroxyalkylations (from epoxides) are illustrated in Scheme 86. 

The addition of organolithiums u thylethylamine forms mainly one dia lion, therefrom chiral amines are avail a-Sulfinyl carbanions also add sopinocampheylborane is an allyl i whereas high-leveled 1,6-asymmetnc 4,5-dicyclohexyl-2-vinyl-1,3-dioxolar Strecker reaction to establish a n capable of creating either a tertiary The peptido-imine 60 proves to be an of aldimines. -" On catalysis of the V-benzhydrylaldimines affords a-amn... 

The addition of a-sulfinyl carbanions to carbonyl compounds followed by further functional group modification has proved to be an efficient and highly stereoselective approach to epoxides, a-aminoketones, a-aminoaldehydes, a-hydroxy esters, and allylic and propargylic alcohols [76-80]. 

An initially formed 7r-aUylpaUadium complex (f s)-12a derived from (Rs)-iE)-8 would be equilibrated into the more stable 7r-allyl systems (/ s)-12b,c in the most preferred rr-allyl system, (/ s)-12c, with the iyn-arylsulfinyl group at Ci and the yn-substituent at C3, the paUadium-phosphine moiety is orientated at the sterically less crowded upper side (the lone pair side of the sulfinyl group) in the electronically most advantageous conformation with the sulfinyl sulfur-oxygen bond coplanar to the rr-allyl system. The intramolecular substitution of the carbanion in (2 s)-12c occurs at C3 of the allyl site from the opposite side of the palladium in a highly stereoselective fashion to afford (S,Rs)-(E)-10 with high de. 

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