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Sulphinates chiral

Sulphinates 60-70 - see also Alkanesulphinates, Arenesulphinates, Thiosulphinates ally - see Allyl sulphinates chiral - see Chiral sulphinates photolysis of 1076... [Pg.1205]

The synthesis of chiral dialkyl sulphoxides of high optical purity from dia-stereoisomeric alkanesulphinates has a serious limitation because the sulphinates are not... [Pg.298]

Further utility of the Andersen sulphoxides synthesis is demonstrated by the preparation of optically active unsaturated sulphoxides which were first prepared by Stirling and coworkers359 from sulphinate 276 and the appropriate vinylic Grignard reagents. Later on, Posner and Tang360 prepared in a similar way a series of ( )-l-alkenyl p-tolyl sulphoxides. Posner s group accomplished also the synthesis of (+)-(S)-2-(p-tolylsulphinyl)-2-cyclopentenone 287, which is a key compound in the chiral synthesis of various natural products361 (equation 159). [Pg.299]

Thus, the enantiomeric contents in a pair of sulphoxides can be determined by the NMR chemical shifts in the methine or methylene protons in the two diastereomeric complexes which are stabilized by the hydrogen bond between the hydroxyl and the sulphinyl groups147-151 (Scheme 13). Similarly, the enantiomeric purity and absolute configurations of chiral sulphinate ester can be determined by measuring the H NMR shifts in the presence of the optically active alcohols152. [Pg.564]

The first reductive kinetic resolution of racemic sulphoxides was reported by Balenovic and Bregant. They found that L-cysteine reacted with racemic sulphoxides to produce a mixture of L-cystine, sulphide and non-reduced optically active starting sulphoxide (equation 147). Mikojajczyk and Para reported that the reaction of optically active phosphonothioic acid 268 with racemic sulphoxides used in a 1 2 ratio gave the non-reduced optically active sulphoxides, however, with a low optical purity (equation 148). It is interesting to note that a clear relationship was found between the chirality of the reducing P-thioacid 268 and the recovered sulphoxide. Partial asymmetric reduction of racemic sulphoxides also occurs when a complex of LiAlH with chiral alcohols , as well as a mixture of formamidine sulphinic acid with chiral amines, are used as chiral reducing systems. ... [Pg.296]

The Andersen sulphoxide synthesis is general in scope and a large number of chiral alkyl aryl and diaryl sulphoxides became available from (—)-(S)-276 and other optically active sulphinates " (Table 16). [Pg.298]

The stereospecific conversion of menthyl arenesulphinates into chiral aryl methyl sulphoxides may also be achieved by means of methyllithium . The reaction of methyllithium with diastereoisomerically or enantiomerically pure arenesulph-inamides 283 was found to give optically active aryl methyl sulphoxides 284 (equation 156). The preparation of optically active sulphoxides 285 and 286, which are chiral by virtue of isotopic substitution (H - D and - respectively), involves the reaction of the appropriate non-labelled menthyl sulphinates with fully deuteriated methyl magnesium iodide (equation 157) and with benzylmagnesium chloride prepared from benzyl chloride labelled with carbon (equation 158). [Pg.299]

Backvall and Juntunen and Fuchs and Braish have developed ( )-2-phenylsuphonyl-1,3-dienes prepared under Julia conditions as versatile synthones for a variety of organic transformations103. These dienes undergo facile Diels-Alder reaction and subsequent 1,4-elimination of sulphinic acid by base to generate a new diene (equation 62)103a. An elegant extension of this method is to use chiral sulfinylmaleate which, on Diels-Alder... [Pg.393]

The chirality exhibited by the pyramidal sulphur compounds (e.g. sulphonium salts, sulphoxides and sulphinic esters) should be noted, but cannot be considered within the scope of this book. [Pg.787]

Enantiomeric distinction can also be achieved using chiral solvents without shift reagents. The determination of enantiomeric purity and the assignment of absolute configuration of cyclic and acyclic sulphinate esters has recently been achieved (573) using chiral l-aryl-2,2,2-trifluoroethanols as solvents. Enhanced enantiomeric distinction has been demonstrated using a combination of both a chiral solvent and an achiral LSR. (514)... [Pg.83]

Chiral triazolopyridines have been made by regioselective metalla-tion of triazolopyridines followed by treatment with chiral electrophiles such as R-(+)-menthyl-p-toluene-sulphinate or (—)-fenchone, giving the corresponding chiral sulphoxides as well as the chiral alcohols in very good yields, and 97% ee (07T10479) (Scheme 14). [Pg.219]

In view of their importance in asymmetric synthesis new routes have been developed to chiral sulphoxides and related species. Sulphinates, useful as precursors of chiral sulphoxides, have been prepared in 40-70% enantiomeric excess and the synthesis and dieno-philic properties of the isomeric sulphinyl acrylates (2l8) and (219) (Ar = 4-MeCgH ) have been described. ( )-Vinyl sulphoxides have been prepared in high optical purity via 1-alkynyl... [Pg.403]

Thus, decomposition of (20) gives (18) alone in the solid state, but if isomerization to (21) [the sulphinate of (19)] is allowed to occur (in solution) loss of SOg gives a mixture of diastereoisomers (18) and (19). The interconversion of (20) and (21), which involves epimerization at one of the chiral centres, is proposed to proceed via ionization and an S02-assisted Walden-like inversion at the asymmetric carbon atom as shown in Scheme 4. This is consistent with the observed inability of SO2 to epimerize (18) in non-polar solvents. [Pg.380]

Reactions.—Asymmetric syntheses involving cr-sulphinyl carbanions have been described, including the preparation of /ff-methoxy-)ff-phenylacetaldehyde via a chiral dithioacetal mono-5-oxide anion " and of lactones, -hydroxy-lactones, and esters such as (i )-mevalonolactone. or-Sulphinyl carbanions are intermediates in the reaction of sulphines with carbanions (thiophilic addition) which can lead ultimately to ketones or olefins - (see also Chap. 3, Pt II, p. 162). [Pg.103]


See other pages where Sulphinates chiral is mentioned: [Pg.296]    [Pg.298]    [Pg.299]    [Pg.1197]    [Pg.298]    [Pg.8]    [Pg.45]    [Pg.506]    [Pg.69]    [Pg.121]    [Pg.205]    [Pg.2]   


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