148118-28-9Relevant articles and documents
Synthesis and evaluation of a broad range of chiral sulfides for asymmetric sulfur ylide epoxidation of aldehydes
Aggarwal,Angelaud,Bihan,Blackburn,Fieldhouse,Fonquerna,Ford,Hynd,Jones,Jones,Jubault,Palmer,Ratcliffe,Adams
, p. 2604 - 2622 (2007/10/03)
We have recently developed a catalytic, sulfur ylide mediated process for converting aldehydes into epoxides using benzaldehyde tosylhydrazone sodium salt which decomposes to generate phenyldiazomethane in situ. Although chiral 1,3-oxathianes gave good yields and excellent diastereo- and enantio-control when phenyldiazomethane was employed, only low yields were obtained when using the simplified procedure employing benzaldehyde tosylhydrazone sodium salt. Thus, a range of more robust chiral sulfides based on thianes, thiolanes, and 1,4-oxathianes were designed to achieve high yield and high enantioselectivity. The sulfides all possessed the following features: conformationally locked cyclic sulfide in which only one of the two lone pairs was accessible (not relevant for C2 symmetric substrates); ylide conformation and face selectivity was to be controlled through non-bonded steric interactions. Chirality was introduced from chiral pool materials (camphor, amino acids, lactic acid, limonene, carvone, glyceraldehyde), through enzyme mediated reduction/hydrolysis and through the use of chiral reagents (hydroboration). The sulfide catalysts were tested in the reaction between benzaldehyde tosylhydrazone salt and benzaldehyde to give trans-stilbene oxide. The range of chiral sulfide catalysts derived from camphor gave trans-stilbene oxide in generally good yield (23-95%) and with moderate enantioselectivity (40-76% ee). The range of novel chiral thianes and 1,4-oxathianes gave trans-stilbene oxide again in generally good yield (9-92%) and with moderate enantioselectivity (20-77% ee). The range of C2 symmetric chiral sulfide catalysts based on 5 and 6 membered rings gave trans-stilbene oxide in moderate yield (10-78%) and with variable enantioselectivity (8-87% ee). In none of the cases could high enantioselectivity and high yield be achieved simultaneously. Analysis of the results led us to the conclusion that the moderate enantioselectivity was a result of poor control in the ylide conformation and this led to the design of completely rigid [2.2.1] bicyclic sulfides which finally gave high enantioselectivity and high yield in the epoxidation process.
Synthesis of enantiomerically pure (1R,2R)- and (1S,2S)-2-alkyl-1-phenylsulfonylcyclopropanes using Bakers' yeast
Tanikaga, Rikuhei,Shibata, Noriaki,Yoneda, Takamitsu
, p. 2253 - 2257 (2007/10/03)
Reduction of the ketone 1 with Bakers' yeast gives the alcohol (R)-2 with high enantiomeric excess, and this upon subsequent epoxidation and alkylation with Grignard reagents provides the alcohols (S)-4 without racemisation. Tosylation of the alcohols (S)-4 under common conditions yields the tosylates (toluene-p-sulfonates) (S)-5, whilst under Mitsunobu conditions inversion of configuration takes place giving the tosylates (R)-5. Subsequent treatment of the tosylates (S)-5 and (R)-5 with lithium diisopropylamide leads to cyclization affording the enantiomerically pure cyclopropanes (S,S)-6 and (R,R)-6 in high yields, respectively. The diastereoisomeric alcohol (S)-4f, obtained by methylation of the alcohol (S)-4e, can also be converted into the single stereoisomer (R,R)-6f in enantiomerically pure form.
MICROBIOLOGICAL REDUCTION OF KETO-SULFONES. APPLICATION IN A THREE-STEP SYNTHESIS OF (S)-(+)-β-ANGELICA LACTONE
Robin, Sylvie,Huet, Francois,Fauve, Annie,Veschambre, Henri
, p. 239 - 246 (2007/10/02)
Microbiological reductions of several keto-sulfones led to the corresponding hydroxy-sulfones in moderate to high enantiomeric excess.A three-step synthesis of (S)-(+)-β-angelica lactone from ethyl-4-oxo-3-(phenyl-sulfonyl)pentanoate via the intermediate
