Sulfones chirality

Rearrangements involving sulfones chiral a,j -unsaturated y-sultines. 

Oxaziridines oxidize sulfides to sulfoxides. Again, the A -sulfonyl derivatives seem to be the best oxidizing agents. They react with sulfides at room temperature to produce sulfoxides uncontaminated with sulfones chiral oxaziridines produce chiral sulfoxides. In addition, chiral thiolsulfinates can be obtained from... 

Immobilization of a sulfonated chiral manganese-salen catalyst on a fimctio-nalized Merrifield resin yielded a remarkably active epoxidation catalyst [42]. Its activity and enantioselectivity was examined by epoxidation of 6-cyanochromene, indene, styrene, 4-methylstyrene, and trans-stilbene using m-CPBA/NMO and quantitative yields were obtained in less than 5 min. Enantioselectivities were between 33% (4-methylstyrene) and 96% ee (6-cyanochromene). The same complex was also supported on silica and a layered double hydroxide (LDEI) and the catalytic performances of the systems were compared. Recycling experiments were carried out and the silica-based system showed metal leaching combined with a significant decrease in yield and ee. The layered double hydroxide- and resin-catalysts exhibited a slight decrease in activity and constant ee values in five consecutive reactions. 

A major breakthrough was achieved with transfer hydrogenation catalysts generated from [Ru(Cl2(arene)] and a semi-AT-sulfonated chiral diamine (e.g., AT-to-syl-l,2-diphenyl-l,2-diaminoethane, N N) [19]. With HCOOH/NEtj as donor, enantioselectivities up to 97% were obtained for substrates of types 7 and 8 (s/c 200-1000 tof 83 h ), providing a new general route to alkaloids (Tables 4 and 5). Furthermore, this catalyst exhibited a high chemoselectivity towards the reduction of C=N vs. C=0 functions. As a consequence, imines of type 7 can even be reduced in acetone with <5% production of 2-propanol. 

The sulfonation of bis(8-phenyloctyl)menthylphosphine gave the corresponding sulfonated chiral ligand [11] ... 

Until very recently, the highest ee for a hydroxycarbonylation reaction was just 43%, in the reaction of p-methoxys-tyrene. This reaction made use of the sulfonated chiral diphosphine 28 (Figure 14.7) The reaction proceeded with... 

Phenyl vinyl sulfoxide is chiral Phenyl vinyl sulfone is achiral... 

Verify, by making molecular models, that the bonds to sulfur are arranged in a trigonal pyramidal geometry in sulfoxides and in a tetrahedral geometry in sulfones. Is phenyl vinyl sulfoxide chiral What about phenyl vinyl sulfone ... 

I.5.3.4.2. Diastereofacial Selectivity I.5.3.4.2.I. Chiral a,/i-Unsaturated Sulfones Addition of Enolates and Related Anions... 

The addition reactions of alkyllithium-lithium bromide complexes to a-trimethylsilyl vinyl sulfones that have as a chiral auxiliary a y-mono-thioacetal moiety derived from ( + )-camphor are highly diastereoselective. A transition state that involves chelation of the organolithium reagent to the oxygen of the thioacetal moiety has been invoked. The adducts are readily converted via hydrolysis, to chiral a-substituted aldehydes22. 

The addition of a lithiated dithiane to a chiral a,/J-unsaturated sulfone has been reported, however, the stereochemical outcome and the diastereoselectivity was not addressed20. The addition of (lithiomcthylsulfonyl)benzenc to a chiral y-alkoxy-a-trimethylsilyl-aj-unsaturated sulfone gave exclusively the, vr -adduct1 2 3 4 5 7 8 9 10 11 12. 

Ueno and coworkers49 have developed a procedure for the synthesis of chiral sulfinic acids. Treatment of (R)-( + )-23 with disulfide 24 and tributylphosphine in THF gave (S)-( — )-25. Compound 25 was oxidized with potassium permanganate to the sulfone, which was then reduced to the sulfinic acid, (S)-( — )-26, by treatment with sodium borohydride. Conversion of 26 or an analog to an ester would lead to diastereomers. If these epimers could be separated, then they would offer a path to homochiral sulfoxides with stereogenic carbon and sulfur atoms. 

An example for synthesis of the chiral [l-keto ester 69 is illustrated in equation 64. It involves conjugate addition of the dipotassium / -keto ester 68 to vinyl sulfone 67 followed by in situ quenching with allyl bromide54. The method provides a new procedure to sevenring annulation product 70 that is a potential precursor for (l)-(-)-cytochalasin C. 

Conjugate addition of chiral amines to allenic and acetylenic sulfones has been reported73. The reaction 112 with (—)-ephedrine gives only one of the two possible diastereomeric oxazolines in high yield (equation 89). 

A chirality transfer from the allenic sulfone 154 to the Diels-Alder adducts is observed in the reaction of (+)-(S)-l-(p-tolylsulfonyl)buta-l,2-diene with cyclopentadiene (equation 112), in which the diastereomers 155 and 156 are formed predominantly107. 

The reaction of chiral sulfones 161, derived from (lS)-( + )-10-camphorsulfonyl chloride, with cyclopentadiene gives predominantly the endo adduct in a diastereomeric ratio of 91 9 from which one diastereomer 162 can be isolated in pure form by recrystallization (equation 115)109. 

The enzymatic oxygenation process is of particular value as there is a significant difference in the formation rates of sulfoxides and sulfones. The initial conversion of sulfide to the optically active sulfoxide by an MO is usually very fast compared to the subsequent oxidation step to sulfone, upon which chirality is lost (Scheme 9.26). In many cases, over-oxidation to sulfone is not observed at all when employing MOs. 

Scheme 9.26 Oxygenation of sulfides to chiral sulfoxides and nonchiral sulfones.

Alkyl halides or alkyl sulfates, treated with the salts of sulfinic acids, give sulfones. A palladium catalyzed reaction with a chiral complexing agent led to sulfones with modest asymmetric induction. Alkyl sulfinates (R SO—OR) may be side products. Sulfonic acids themselves can be used, if DBU (p. 1337) is... 

When a sulfonate ester possessing this type of chirality was converted to a sulfone with a Grignard reagent (10-129), inversion of configuration was found. This is not incompatible with an intermediate such as 147 but it is also in good accord with an Sn2 like mechanism with backside attack. 

For a review of the synthetic uses of 3-keto sulfoxides, sulfones, and sulfides, see Trost, B.M. Chem. Rev., 1978, 78, 363. For a review of asymmetric synthesis with chiral sulfoxides, see Solladie, G. Synthesis, 1981, 185. 

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