Sulfinyl substituents

A wide variety of chiral sulfinyl substituents have been employed as chiral auxiliaries on both dienes162 and dienophiles163 in asymmetric Diels-Alder reactions. Carreno and colleagues164, for example, used Diels-Alder reactions of (Ss)-2-(p-tolylsulfinyl)-1,4-naphthoquinone (249) to separate racemic mixtures of a wide variety of diene ena-tiomers 250a and 250b via kinetic resolution and to obtain enantiomerically enriched... 

Clayden et al. have shown recently that 2-arylpyridines and 1-aryliso-quinolines 286 can adopt one of two axial conformations when they are substituted in the 2-position of the aryl by a chiral sulfinyl substituent. The preferred conformer is the one in which the nitrogen of the heterocycle is opposite to the sulfoxide S-O bond in order to minimize the dipole repulsion (09JA5331). 

Chiral Alkoxy, Amino ethyl and Sulfinyl Substituents.265... 

This chapter will be divided into two distinct parts. Firstly, general methods for making Ti -arene chromium tricarbonyl complexes will be discussed. Particular attention will be paid to complexes bearing sulfinyl substituents and protocols for their synthesis will be given. The second part will deal with enantiopure or enriched complexes. Examples of diastereoselective syntheses of optically pure 1,2-disubstituted complexes with amino and hydroxyl groups at the two benzylic positions will be presented. 

More recently, Davis and co-workers developed a new method for the asymmetric syntheses of aziridine-2-carboxylates through the use of an aza-Darzens-type reaction between sulfinimines (N-sulfinyl imines) and a-haloenolates [62-66]. The reaction is highly efficient, affording cis- N-sulfmylaziridine-2-carboxylic esters in high yield and diastereoselectivity. This method has been used to prepare a variety of aziridines with diverse ring and nitrogen substituents. As an example, treatment of sulfinimine (Ss)-55 (Scheme 3.18) with the lithium enolate of tert-butyl bromoacetate gave aziridine 56 in 82% isolated yield [66],... 

Addition of metalated, enantiomerically pure a-sulfinyl dimethylhydrazones (e.g., 9) to racemic a-chiral aldehydes 10 proceeds with good to excellent diastereo- and enantioselectivi-ty12. Diastereomeric ratios increase with increasing steric demand of the acetaldehyde substituent R1 compared to the methyl group, and each diastereomer is obtained with high enantiomeric excess. In the aldol-lype addition to 2-phenylpropanal, one of the four possible stereoisomers is formed selectively. The relative (syn) and absolute (R.R) configuration is in accord with Cram s and related rules as well as H-NMR data of closely related compounds. 

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. 

The addition of the dianion of /j-sulfmylcarboxylic acids to carbonyl compounds leads to the formation of the corresponding hydroxy derivatives which undergo spontaneous eyclization to give y-lactones. It was found that when optically active ( + )-(/ )-3-(4-methylphenylsulfinyl)pro-panoic acid is used for the reaction, the corresponding diastereomeric /i-sulfinyl-y-lactones are formed in a ratio which is dependent on the substituents of the carbonyl component. However, the diastereoselectivity was always moderate. 

Thiirane oxides (3 x = 1) were rather rare and not well characterized until about 20 years ago20. Since 1965 synthetic methods for their preparation have been consistently and systematically explored2. They are rather thermodynamically stable compounds— compared to their closely-related thiirane dioxides—provided they have an anticonfiguration with respect to the substituents and the sulfinyl oxygen. Also they are more resistant than the corresponding sulfones toward ring opening by either nucleophiles or electrophiles. 

The electronic effects of many substituents have been examined by studies of PMR118,119 sulfinyl and sulfonyl groups have been included in some of these. For example, Socrates120 measured the hydroxyl chemical shifts for 55 substituted phenols in carbon tetrachloride and in dimethyl sulfoxide at infinite dilution, and endeavored to... 

However, in more recent years it has become usual to employ ar or crR-type constants, either together in the dual substituent-parameter equation or individually in special linear regression equations which hold for particular infrared magnitudes. In this connection a long series of papers by Katritzky, Topsom and their colleagues on Infrared intensities as a quantitative measure of intramolecular interactions is of particular importance. We will sample this series of papers, insofar as they help to elucidate the electronic effects of sulfinyl and sulfonyl groups. 

Meyers and coworkers141 measured the pKa values of a number of arylthio-, arylsulfinyl-and arylsulfonyl-phenols. From their few results relating to the effects of 4 - R on 4-OH, Hogeveen138 inferred that relative influence of substituents was about the same in the three series, contrasting with what he had found in his various series of acrylic acids. He attributed this to the compensation of the polarizability effect (see above) by the influence of a(pd) conjugation in the anions of the sulfinyl and sulfonyl series. Meyers and coworkers141 were more interested in the effect of moving the OH from the 4- to the 2-position (see Section III.D). 

The effect of sulfur-containing substituents on free radicals appears to be a topic of current interest, so we will discuss it briefly insofar as it concerns sulfinyl and sulfonyl groups. Our discussion will refer mainly to a few recent papers, which usually contain copious references to earlier work see also Block247. 

Accordingly, there have been numerous studies on the stereochemistry of these a-sulfinyl carbanions56-77. Representative data on the reactions of a-lithiosulfoxides derived from benzyl sulfoxides with some electrophiles are listed in Table 13. Although the stereochemistry depends on the substituent on the sulfinyl function, the diastereomeric ratio remains the same regardless of the electrophile used for each sulfoxide. 

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