Benzyl methyl sulfoxide

In the case of the condensation of benzyl methyl sulfoxide with bcnzaldchydc (40% yield), the diastereomeric ratio of four enantiomeric (S-sulfinyl alcohols after immediate workup is 41 19 8 32 . 

The relative ease of H/D exchange of the methylene protons of benzyl methyl sulfoxide is markedly influenced by the nature of the base and the solvent used, as shown in Table 12. The data reveal that rather high stereoselectivities can be observed when alkyllithium-THF is used. 

TABLE 12. Relative rates of H/D exchange of the diastereotopic protons in benzyl methyl sulfoxide and relative amount of 40 and 41 formed upon quenching of a-lithiobenzyl ethyl sulfone with D20 (after Reference 56)... 

Optically pure (S)-benzyl methyl sulfoxide 139 can be converted to the corresponding a-lithio-derivative, which upon reaction with acetone gave a diastereomeric mixture (15 1) of the /S-hydroxysulfoxide 140. This addition reaction gave preferentially the product in which the configuration of the original carbanion is maintained. By this reaction, an optically active epoxy compound 142 was prepared from the cyclohexanone adduct 141181. Johnson and Schroeck188,189 succeeded in obtaining optically active styrene oxide by recrystallization of the condensation product of (+ )-(S)-n-butyl methyl sulfoxide 143 with benzaldehyde. 

Asymmetric oxidation of sulfides to sulfoxides occurs in the presence of chiral catalysts. It was found (53) that oxidation of benzyl methyl sulfide with iodine suspended in (i )-2-methyl-2-phenylsuccinate 33 buffer gives optically active benzyl methyl sulfoxide 34 having 6.35% optical purity. Much higher asymmetric... 

Similar differentiation between enantiomers by means of NMR can also be achieved by the use of chiral lanthanide shift reagents (243). Tris-[3-(heptafluoropropylhydroxymethylene)-d-camphorato] -europium was used for the first time (244) for determining the enantiomeric content of benzyl methyl sulfoxide 34. The enantiomeric composition of the partially resolved methyl p-tolyl sulfoxide 41 was estimated using tris-[3-(r-butylhydroxymethylene)-c -camphorato]-europium (245). Another complex of europium, tris-[3-(trifluoro-methylhydroxymethylene)-c -camphorato] europium (TFMC), in contrast to those mentioned above, was effective in the differentiation of various enantiomeric mixtures of chiral sulfinates (107), thiosul-finates (35), and sulfinamides (246). 

Durst and co-workers (309) investigated in detail the stereochemistry of deuteration and methylation of carbanions derived from optically active (+)-(5)-benzyl methyl sulfoxide 34 and (+)-(i )-benzyl t-butyl sulfoxide 290. The reactions, which allowed the extent of asymmetric induction on the a-carbon atom as well as the stereochemistry of deuteration and methylation to be determined, are summarized in Schemes 30 and 31. 

Bromination of (-)-(5 )-benzyl methyl sulfoxide 34 with bromine in pyridine affords a mixture of two regioisomers a-bromomethyl benzyl sulfoxide 328 and a-bromobenzyl methyl sulfoxide 329, in a molar ratio of 3 2 (325). Oxidation of thp latter gives the corresponding sulfone (-)-(S)-330, the absolute configuration of which was determined by X-ray analysis. In this context, it is interesting to point out that the formation of the sulfoxide 328 is accompanied by retention at sulfur, whereas 329 is formed with inversion at sulfur. 

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. 

Dimsyl anion fails to undergo SrnI reactions with aryl halides,134,143 and the occurrence of fragmentation processes similar to those in equations (11) and (45) have been used to explain this failure,143 correcting the earlier, falacious claim that dimsyl anion and halobenzenes react to give benzyl methyl sulfoxide in high yield.144... 

The Orsay group discovered that addition of 4 mol equiv. of isopropanol to the Padua complex (Ti(0-i-Pr)4/(i ,7 )-DET = 1 4) gave a complex that can be used in catalytic quantities (10 mol % with respect to sulfide) in the sulfoxidations with cumene hydroperoxide [39,40], With this catalyst system, which needs the presence of 4A molecular sieves, enantioselectivities in the range of 90% ee have been achieved for the preparation of various aryl methyl sulfoxides. Even benzyl methyl sulfoxide was obtained with 90% ee. 

A. Rauk, E. Buncel, R. Y. Moir, and S. Wolfe,/. Am. Chem. Soc., 87,5498 (1965). Hydrogen Exchange in Benzyl Methyl Sulfoxide. Kinetic and Spectroscopic Nonequivalence of Methylene Protons. 

It should be noted that benzyl methyl sulfoxide was included without the recognition of its chirality (entry 7 in Table 1) [23]. Using single-crystal X-ray analyses... 

Figure 14 Inclusion compound of benzyl methyl sulfoxide by 1. (a) Layer structure, (b) Packing (CPK model) and schematic representation of both recognition sites. For clarity, phenyl groups of 1 and guest are unshaded and gray, respectively.

Toda, F., Tanaka, K., and Okuda, T. (1995) Optical Resolution of Methyl Phenyl and Benzyl Methyl Sulfoxides and Alkyl Phenylsulfinates by Complexation with Chiral Host Compounds Derived from Tartaric Acid, J. Chem. Soc., Chem. Commun., 639-640. 

It should be noted that benzyl methyl sulfoxide was included without the recognition of their chirality (entry 7 in Table 4).26 By single crystal X-ray analyses of this inclusion compound, it was elucidated that the molecules of 1 form the layer structure similar to the one of the above alkyl phenyl sulfoxide-inclusion crystals, and the sulfoxides are included between these layers. There are two different recognition cavities on the upper side for its S enantiomer and on the lower side for its K enantiomer. The upper side cavity can be illustrated by motif A, and the lower side one by motif B in Figure 16. 

Figure 16. Inclusion compound of benzyl methyl sulfoxide by 1. (a) Layer sturcture. (b)...

Akazome, M., Ueno, Y., Ooiso, H., and Ogura, K. (2000) Enantioselective Inclusion of Methyl Phenyl Sulfoxides and Benzyl Methyl Sulfoxides by (i )-Phenylglycyl-(i )-phenylglycine and the Crystal Structures of the Inclusion Cavities, J. Org. Chem. 65, 68-76. 

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