R - -Methyl p-Tolyl Sulfoxide

Only relatively few nucleophilic substitution reactions at sulfur proceed with retention. Oae found that (R)-(+)-methyl p-tolyl sulfoxide exchanged 180 with dimethyl sulfoxide at 150 °C much faster than it racemized thus, the exchange took place with retention. A cyclic intermediate, 136, was proposed to account for this behavior12,147. The same sulfoxide was found to react with N, JV -ditosylsulfurdiimide, 137, with either retention or inversion depending on the reaction conditions. Christensen148 observed retention in benzene whereas Cram and coworkers149 found that inversion took place in pyridine. A four-membered ring intermediate, 138, was postulated to account for the retention, whereas a... 

Carbanions derived from optically active sulfoxides react with esters, affording generally optically active )S-ketoesters ° . Kunieda and coworkers revealed that treatment of (-t-)-(R)-methyl p-tolyl sulfoxide 107 with n-butyllithium or dimethy-lamine afforded the corresponding carbanion, which upon further reaction with ethyl benzoate gave (-l-)-(R)-a-(p-tolylsulfinyl)acetophenone 108. They also found that the reaction between chiral esters of carboxylic acids (R COOR ) and a-lithio aryl methyl sulfoxides gave optically active 3-ketosulfoxides The stereoselectivity was found to be markedly influenced by the size of the R group of the esters and the optical purity reached to 70.3% when R was a t-butyl group. 

No stereoselectivity was observed in the formation of a 1 1 diastereomeric mixture of 2-hydroxy-2-phenylethyl p-tolyl sulfoxide 145 from treatment of (R)-methyl p-tolyl sulfoxide 144 with lithium diethylamide . However, a considerable stereoselectivity was observed in the reaction of this carbanion with unsymmetrical, especially aromatic, ketones The carbanion derived from (R)-144 was found to add to N-benzylideneaniline stereoselectivity, affording only one diastereomer, i.e. (Rs,SJ-( + )-iV-phenyl-2-amino-2-phenyl p-tolyl sulfoxide, which upon treatment with Raney Ni afforded the corresponding optically pure amine . The reaction of the lithio-derivative of (-t-)-(S)-p-tolyl p-tolylthiomethyl sulfoxide 146 with benzaldehyde gave a mixture of 3 out of 4 possible isomers, i.e. (IS, 2S, 3R)-, (IS, 2R, 3R)- and (IS, 2S, 3S)-147 in a ratio of 55 30 15. Methylation of the diastereomeric mixture, reduction of the sulfinyl group and further hydrolysis gave (—)-(R)-2-methoxy-2-phenylacetaldehyde 148 in 70% e.e. This addition is considered to proceed through a six-membered cyclic transition state, formed by chelation with lithium, as shown below . ... 

Esterification of p-toluenesulfinic acid with (- )-menthol gives a mixture of two diastereomers, which equilibrate to the pure (-)-menthyl (S)-p-toluenesulfinate diastereomer in the presence of hydrochloric acid (80% yield). The report includes an improved procedure for reaction of 1 with CH,MgI to give (R)-( + )-methyl p-tolyl sulfoxide.1... 

Little work has been done in this area with Ru catalysts. CM-A-[Ru(0)(py)(bpy)3] V water-CH3CN was used for the stoicheiometric oxidation of methyl-p-tolyl sulfide to (R)-methyl-p-tolyl sulfoxide with an e.e. of ca 15% [121],... 

This reagent (pure) can be obtained by reaction of (R)-(+)-methyl p-tolyl sulfoxide with NCS in the presence of K2C03 followed by several recrystallizations. 

The reaction of 60 with an excess of alkane- or arenesulfinyl chloride affords sulfinate esters 61-(R) and 61-fSj in good yields and moderate selectivity [(4-10) 1]. The diastereomeric sulfinates were separated either by crystallization or by column chromatography. Two arene- and two alkanesulfinates were prepared optically pure by the reported method (Scheme 18). The major isomer of the methanesulfinate was used in the synthesis of o.p. (R) methyl p-tolyl sulfoxide 62 in 76% yield, while the p-toluenesulfinate was used to obtain the (S)-p-phenoxyphenyl p-tolyl sulfoxide 63 in 70% yield. 

Preparative Methods conveniently prepared - by reaction of the magnesium enolate of r-butyl acetate (readily made with Bromomagnesium Diisopropylamide) with (-)-(lR,2S,5R)-Menthyl (S)-p-Toluenesulfinate (eq 1). It was also made in 91% yield by reacting a solution of Lithium Diisopropylamide with (R)-(+)-methyl p-tolyl sulfoxide and 7-butyl carbonate (eq 2). It should be noted that asymmetric oxidation of 7-butyl 2- p-tolylsulfinyl)acetate with a modified Sharpless reagent gave a... 

Related Reagents. (R)-(+)-r-Butyl 2-(p-Tolylsulfinyl)-propionate (R)-(+)-Methyl p-Tolyl Sulfoxide (R)-(+)-Phenyl (p-Toluenesulfinyl)acetate. 

Preparation.1 The reagent is prepared from (R)-( + )-methyl p-tolyl sulfoxide as shown. o... 

Synthesis of optically active alcohols.1 For asymmetric synthesis of alcohols, the carbanion salt (2) is generated from optically active (R)-methyl p-tolyl sulfoxide (I).2 The optically active carbanion reacts with benzaldehyde (3) to give a 1 1 diastereomeric mixture of 2-hydroxy-2-phenylethyl p-tolyl sulfoxides (4a) and (4b) in 84% yield-These can be separated by silica gel chromatography and fractional crystallizations to give (4a, oq, + 91.7°, 17% yield) and (4b, aD + 202.8°, 15.5% yield). Raney nickel desulfurization of (4a) and (4b) gives (SH-)-l-phenylethanol (5a, aD — 42.6°) and R-(+)-l-phenylethanol (5b, aD +42.1°), respectively, in about 60% yield. Since the specific rotation of optically pure (5b) is aD +43.5°, alcohols of high optical purity can be obtained in this way. 

Enantlomerically pure (R)-(+)-methyl p-tolyl sulfoxide, prepared from (-)-menthyl p-tolylsulfinate,3 4 was described with the following specific rotations [a]g +145.5° (acetone),3 [a]g5 +168° (acetone, e 1.8), [a]g +189° (CHClj, a 1). The submitters checked a sample prepared3,4 and kindly provided by Professor G. Solladle (Strasbourg), which was recrystal 11zed from hexane [a]g +146° + 1 (acetone, e 1), mp 76-77°C. HPLC analysis carried out on a chiral stationary phase shows the absence of the enantiomer (Dr. Tambute, private communication). The same analysis shows that the product obtained by the procedure described above is of 99.5% ee. 

The required ketosulfoxide 69 (Scheme 15) was obtained in two steps in a one-pot procedure from 1,4-dimethoxybenzene (66). Ortho Hthiation of 66, lithium-copper exchange, and addition to methyl acrylate gave ester 67. Reaction of the anion obtained from (R)-methyl(p-tolyl)sulfoxide (68) [89] by treatment with LDA, with ester 67 afforded ketone 69. Diastereoselective addition of diethylaluminum cyanide to the carbonyl group of 69 [90] furnished sulfinylcyanohydrin 70 as the sole product. The (S) configuration of the new stereogenic center was inferred from the previous studies of acycUc P-ketosulfoxides [91,92]. 

R)-(+)-Methyl p-tolyl sulfoxide allowed to react at -20 to -10 with Li-diethyl-amide in tetrahydrofuran, then N-benzylideneaniline added (Rg,SQ)-(+)-N-... 

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