A new asymmetric organocatalytic synthesis of spirocyclopropaneoxindoles has been developed. The method is based on the Michael addition of N-Boc-protected 3-chlorooxindole to unsaturated 1,4-dicarbonyl compounds, affording trans-substituted spirocyclopropaneoxindolederivatives in high diastereo- and enantioselectivity.
Reaction of N-fluoropyridinium salts with wittig reagents: A novel and convenient approach to symmetric trans-olefins
作者:Alexander S. Kiselyov
DOI:10.1016/0040-4039(94)88397-1
日期:1994.11
N-fluoropyridinium salts were found to react with Wittig reagents containing electron-withdrawing groups to give olefins in 47–83% yield. The mechanism of this conversion is believed to involve single-electron transfer from Wittig reagent to N-fluoropyridinium cation.
The organocatalytic Michael addition of malonates to symmetric unsaturated1,4-diketones catalyzed by thiourea and squaramide derivatives with Cinchona alkaloids afforded the formation of a new C-C bond in high yields (up to 98%) and enantiomeric purities (up to 93%). The absolute configuration of the product was suggested from comparison of the experimental and calculated VCD spectra of the reaction