Self-catalytic Michael reaction of enolizable carbonyl compounds. A facile route to α-methylene-δ-valerolactones
作者:Henryk Krawczyk、Marcin Śliwiński
DOI:10.1016/j.tet.2003.09.039
日期:2003.11
2-phosphono-5-oxoalkanoates 3 were prepared by the Michaelreaction of enolizable carbonylcompounds with the acrylate 1. The corresponding 2-phosphono-5-oxoalkanoic acids 4 were converted into α-phosphono-δ-valerolactones 6. The products were shown to be useful substrates for the synthesis of α-methylene-δ-valerolactones 7 by the Horner–Wadsworth–Emmons reaction.
chiral imines 2, 9 and the acrylate 3. Reduction of the carbonyl group of the resulting adducts 4 and 10 with KBH 4 followed by lactonization and HWE reaction with formaldehyde yielded the lactones 7 and 13 as mixtures of diastereoisomers. Diastereoselectivity in the reduction of chiral 5-oxoalkanoic acids 4 and 10 was improved by combination of metal salt and hydride reducing agent.
Nitroalkanes as nucleophiles in a self-catalytic Michael reaction
作者:Henryk Krawczyk、Wojciech M. Wolf、Marcin Śliwiński
DOI:10.1039/b209302m
日期:——
A simple, effective procedure for the preparation of 4-nitroalkanoates 6–9 by the Michael reaction of nitroalkanes 2–5 with the acrylate 1 is described. The primary nitro adduct 6 undergoes isomerization to hydroxamic acid 10 while heated in boiling nitromethane. Consecutive reactions of the latter compound lead to the formation of N-hydroxysuccinimide 11 and its N-ethoxy derivative 12. The spontaneous Nef reaction of the mother 4-nitrobutanoic acid 15 gives N-hydroxysuccinimide 14. The analogous reaction of secondary nitroalkanoic acids 16 and 17 provides 4-oxoalkanoic acids 18 and 19, respectively. Intramolecular participation by the carboxylic acid group in the Nef reaction is proposed.
Indoles as Nucleophiles in a Self-Catalytic Michael Reaction
作者:Henryk Krawczyk、Marcin Śliwiń
DOI:10.1055/s-2002-33105
日期:——
C-3 Substituted indoles 7a-c were regioselectively synthesized in high yields by reacting indole 2 and electron-rich indoles 3,4 with acrylate 1. Additions of electron-deficient indoles 5,6 to the acrylate 1 gave N-substituted indoles 9a,b.
Electron-rich hydroxyarenes undergo self-catalytic Michael reaction with the dicyclohexylammonium acrylate 1. The regiochemistry of this reaction is markedly dependent on structural features of the starting hydroxyarenes. While at 25 °C and in nonpolar solvents phenol and most of its monosubstituted derivatives are converted into the corresponding O-adducts, conjugate addition of disubstituted phenols and naphthols leads to the C-adducts exclusively. An analogous reaction pattern is observed with the dicyclohexylammonium acrylate 2 as the Michael acceptor.