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,... 

The first example of SO photoextrusion to the best of our knowledge is that of Kellogg and Prins in 1974 with the dihydrothiophene derivatives 137 [64]. The analogous sulfones undergo stereospecific concerted thermal extrusion but were found photochemically to lead to some loss of stereochemistry in the diene, attributed to stepwise a-cleavage. The sulfoxides also quantitatively gave dienes 138 of mixed stereochemistry. This was taken to imply a biradical intermediate, presumably the initial allyl-sulfinyl biradical. No intermediates or other products (e.g., vinyl episulfoxides, sultenes) were observed. In contrast, episulfides were observed for photolysis of the analogous sulfides. 

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

The Stockman group has also studied reactions between the same imines and allyl sulfonium ylides (first reported by Hou and Dai [45]) [46], N-Sulfinyl vinylazir-... 

Sulfinyl oxiranes 2 can be desulfurized with butyllithium at very low temperature to give oxiranes with retention of configuration as a result of a ligand exchange at sulfur (see also Table 6). However, with a benzylic substituent R1, an excess of butyllithium may at higher temperatures induce an elimination to an allylic alcohol. 

Optically active allylic alcohols can only be prepared from optically active sulfinyl epoxides when the created double bond is conjugated to an aromatic system. One example is described below29. 

From studies on the addition of racemic allylic sulfoxide anions of 3-substituted l-(phenyl-sulfinyl)-2-propenes to racemic 4-tcrr-butoxy-2-cyclopentenone, it was found that (El-allylic sulfoxides give. vyw-products, and (Z)-allylic sulfoxides give anti-productsx. 

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 the reaction of 88 with -phenethyl bromide, l-phenethyl-3-phenylpropyl methyl sulfoxide and bis-3-phenylpropyl sulfoxide, besides 3-phenylpropyl methyl sulfoxide are obtained . Sulfoxides, bearing a -hydrogen to the sulfinyl function, give olefins upon thermolysis. Utilizing this reaction, Trost and Bridges alkylated benzyl phenyl sulfoxide, 3,4-methylenedioxybenzyl phenyl sulfoxide, phenylthiomethyl phenyl sulfoxide, phenylsulfinylmethyl phenyl sulfoxide and cyanomethyl phenyl sulfoxide with alkyl, allyl and benzyl halides and subjected these sulfoxides to thermolysis, obtaining olefins in one-pot processes. 

By modification of the elegant method of preparation of optically active sulfinates previously reported by Mikolajczyk and coworkers , an efficient stereospecific method for the conversion of readily available optically active sulfinamides to optically active sulfinates of inverted configuration at the sulfinyl function, has been recently reported by Hiroi and coworkers . The same authors subsequently reported the thermal rearrangement of several optically active cis- and trans-y-substituted allylic p-toluenesulfinates to optically active chiral sulfones with high stereoselectivity. For example, trans and cis (S)-( — )-crotyl p-toluenesulfinates rearranged to optically active (S)-(-l-)- and (R)-( — )-a-methylallyl p-tolyl sulfone, respectively (equation 19). 

Diastereoselective allylation under aqueous Barbier conditions of a-amino aldehydes with the chiral building block (Ss)-3-chloro-2-(p-tolylsulfinyl)-l-propene to give enantiomerically pure sulfinyl amino alcohols in good yields and with high diastereoselectivity was reported (Eq. 8.34).73... 

Die Reaktion von aliphatischen N-Sulfinyl-aminen mit Allyl-halogeniden in Gegenwart von nukleophilen Basen wie Lithium-triphenylmethid Oder Kalium-tert.-butoxid fuhrt zur Bildung von 4-Amino-l-alkenen1. 

Butenyloxy)-1 -fluoro-1 -phenyl-sulfinyl- EI0b2. 207 (OH O - Allyl)... 

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). 

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