A-sulfinyl acetate

SoUadid has introduced a-sulfinyl acetates as reagents for asymmetric aldol reactions.Compound (211) is prepared in good optical purity from the menthyl ester of p-tolylsulfinic acid. The magnesium enolate of (211), prepared by reaction of the sulfrnyl ester with r-butylmagnesium bromide, reacts with aldehydes and ketones to give diastereomeric mixtures of a-sulfinyl-3-hydroxy esters (Scheme 13). No... 

The AA-sulfinyloxazolidinone reagents were found to be useful in the asymmetric synthesis of a-sulfinyl acetate (18), sulfinate esters (19) and sulfinamides (20). 

Enzyme-mediated hydrolysis of some racemic co-arenesulfinylalkanoic methyl esters, ArSO(CH2) COOMe, using Corynebacterium equi has led to a kinetic resolution in which the unreacted sulfinyl esters are enriched in one enantiomer at the sulfoxide center49. The enantiomeric purity of unreacted sulfinyl acetates and propionate ranges from 90 to 97%. 

The stereoreactivity of the methylene protons of er -butyl (4-methylphenylsulfinyl)acetate is in sharp contrast with the highly stereospecific behavior of the methylene protons of benzyl methyl sulfoxide. An NMR study of phenylsulfinylacetic acid showed that the reactivity of these two diastereotopic protons is comparable83. These protons are even magnetically equivalent in deuterium oxide solution. The diastereoselectivity of the alkylation of a-sulfinyl carboxylic esters is poor, moreover, the reaction proceeds only when butyllithium, ferz-butyllithium or lithium diethylamide is used as the base in the preparation of the carbanion82. 

The Pummerer reaction of sulfinyl compounds involves the formation of an a-functionalized sulfide [244, 245] from a sulfoxide. Acetic anhydride is commonly used as the electrophile, which adds to the sulfoxide to yield a sulfonium salt, and the rearrangement occurs through successive formations of an ylide (rate-determining step) and an alkylidene sulfonium, trapped by a nucleophile, or stabilized by a proton loss with formation of a vinyl sulfide. 

Acetalization of thiochroman-3-one gives a 1 1 diastereomeric mixture and subsequent oxidation with Davis reagent, W-(phenylsulfonyl)(3,3-dichlorocamphoryl)oxaziridine, yielded the sulfoxides each with a 4 1 enantioselectivity. Chiral chromatographic separation of the diastereomers preceded isolation of the major enantiomers. (3-Elimination and isomerization of the double bond then produced the individual thiochromene 1-oxide diastereomers. The generation of an a-sulfinyl carbanion effects the cleavage of one of the acetal C-O bonds with the protected diol released in a final ozonolysis step. The stereochemical results indicate that it is the C-O bond syn to the sulfoxide function that is cleaved (Scheme 63) <1996TA29>. 

The chlorination of an alkyl 2,4-dinitrobenzenesulfenate (180) in acetic acid leads to an intimate sulfoxonium ion pair (181) which may lose a sulfinyl chloride fragment before or after solvation174 177. The chloride-acetate ratio decreases sharply in the presence of added lithium perchlorate, a manifestation of a special salt effect. Since... 

The Knoevenagel and Wittig type reactions have been used for the creation of the 6-bond. The condensation of octadecanal with methyl p-(chlorophenyl)sulfinyl acetate in the presence of piperidine afforded the corresponding acetate after acetylation of the hydroxy group which, after subsequent molibdenum-catalyzed elimination, gives the dienic ester as a 4 1 E,E E,Z mixture. After final amidation, the amide trichonine (13) [40] is obtained (Scheme 2). A similar strategy has been used for the synthesis of piperovatine (21) with total E,E-stereoselectivity [41]. 

Fig.l Frequency of detection of herbicides (red bars) and their transformation products (blue bars) in samples collected from 51 US Midwestern streams during late spring runoff (A) and harvest season runoff (B) [34]. ESA - ethane sulfonic acid OXA - oxanilic acid SAA - sulfinyl acetic acid... 

Chirality need not reside on a sp carbon atom to be recognized by PSL but can be located on a sulfur atom (Scheme 2.64). Thus, optically pure aryl sulfoxides were obtained by lipase-catalyzed resolution of methyl sulfinyl acetates [458] in a biphasic medium containing toluene. The latter compounds are important starting materials for the synthesis of chiral allylic alcohols via the SPAC reaction. 

The Pummerer rearrangement was reported by Rudolf Pummerer in 1909 when he published a paper in Chemische Berichte. Earlier in the same year, Smythe had reported the reaction of dibenzyl sulfoxide 3 with acetic anhydride and hydrochloric acid to give benzaldehyde 4 and thioacetal 5, among other products. Smythe was apparently unable to explain the product distribution, which was then left to Pummerer do so in his much-cited paper later that year. Pummerer published the reaction of sulfinyl acetic acid 6 with hydrochloric acid to give glyoxylic acid 7. The formal oxidation of the... 

Chloro-a,/3-unsaturated aldehydes condense with ammonium thiocyanate to give isothiazoles (76EGP122249). 2,3-Diphenylcyclopropenone reacts with iV-sulfinyl-cyclohexylamine in the presence of nickel tetracarbonyl to give the isothiazolin-3-one 1-oxide (197) (79SST(5)345). Cholesteryl acetate reacts with trithiazyl trichloride in pyridine to give the isothiazolo steroid (198) (77JCS(P1)916). 

Esters and amides may be sulfinylated. Addition of a mixture of t-butyl acetate and sulfinate ester 19 to a THF-ether solution of magnesium diisopropylamide led to the formation of (R)-(+)-f-butyl p-toluenesulfinylacetate (49) in 90% yield (equation 14)7. t-Butyl propanoate and butanoate also underwent this sulfinylation to give 50 and 51 in yields of 68 and 45%, respectively83. The diastereomeric ratio was 1 1 for 50 and 3 7 for 51. These esters may also be obtained by alkylation of 49. Similarly, treatment of a-lithio-A, A -dimethylacetamide with sulfinate ester 19 gave (R)-( + )-N, Ar-dimethyl-p-toluene-sulfinylacetamide (52) (equation 15)84. 

Among the oxyacids of sulfur the predilection to form an anhydride with a sulfur-sulfur bond, rather than one with an oxygen bridge between the two sulfurs, is not restricted to sulfenic acids. We will see in a subsequent section that sulfinic acids also do this. Their anhydrides have the sulfinyl sulfone structure. RS(0)S02R, rather than RS(0)0S(0)R. What is unique about the sulfenic acid-thiolsulfinate system, however, is the fact that the anhydride (thiolsulfinate) is strongly preferred thermodynamically over the acid at equilibrium. With any other type of common acid the reverse is true, of course. The uniqueness of the sulfenic acid-thiolsulfinate situation can perhaps best be appreciated by realizing that, if the same stability relationship between acid and anhydride were to exist for carboxylic acids, acetic acid would spontaneously dehydrate to acetic anhydride ... 

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