One-pot synthesis of (S)-4-isopropyl-2-p-toluene-4,5-dihydro-[1.2λ6,3]oxathiazole 2-Oxides: Efficient precursors of optically active sulfoximines
摘要:
The title compounds were prepared from p-toluenesulfinyl chloride and (S)-O-trimethylsilyl valinol without isolation of intermediates. Key step in the synthesis is the fluoride-induced cyclisation of sulfonimidoyl chlorides yielding the crystalline sulfonimidates 4 and 5 as a mixture of enantiomerically pure diastereomers which were easily separable by column chromatography or just simple crystallisation. Their reactions with either organolithium or Grignard reagents offer a convenient entry to enantiomerically pure sulfoximines in high yields.
A series of chiral amino alcohols transformed into the formamidine derivative of 1, 2, 3, 4-tetrahydroisoquinolines were evaluated as chiral dipole-stabilized anions. Alkylation with alkyl halides provided the 1-alkyl-l, 2, 3, 4-tetrahydroisoquinolines in both excellent yield and enantiomeric purity.
enamide of a chiral iminederivedfrom a ketone and (S)-valinol or (S)-t-leucinol undergoes addition to 1-alkene to generate a gamma-zincioimine intermediate, which reacts with a carbon electrophile to give upon hydrolysis an optically active alpha-substituted ketone in good yield. The stereoselectivity of the addition reaction may reach 99% for the reaction of a cyclohexanoneimine with ethylene.
One-pot synthesis of (S)-4-isopropyl-2-p-toluene-4,5-dihydro-[1.2λ6,3]oxathiazole 2-Oxides: Efficient precursors of optically active sulfoximines
作者:Michael Reggelin、Heinz Weinberger
DOI:10.1016/s0040-4039(00)60906-1
日期:1992.11
The title compounds were prepared from p-toluenesulfinyl chloride and (S)-O-trimethylsilyl valinol without isolation of intermediates. Key step in the synthesis is the fluoride-induced cyclisation of sulfonimidoyl chlorides yielding the crystalline sulfonimidates 4 and 5 as a mixture of enantiomerically pure diastereomers which were easily separable by column chromatography or just simple crystallisation. Their reactions with either organolithium or Grignard reagents offer a convenient entry to enantiomerically pure sulfoximines in high yields.
Simple amino silyl ether organocatalyst for asymmetric hetero Diels–Alder reaction of isatins with enones
component system comprising of a primary β-amino silyl ethers as an organocatalyst and N-protected amino acids as a co-catalyst put together worked as an efficient organocatalyst system in the heteroDiels–Alderreaction of isatins with enones affording the chiral spirooxindole-tetrahydropyranones in good chemical yields and stereoselectivities (up to 94%, up to dr 78:22., up to 85% ee).