- Highly regioselective alkylation at the more hindered α-site of unsymmetrical ketones by use of their potassium enolates. A comparative study with lithium enolates
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Alkylation of regioisomeric potassium enolates 4 and 6 obtained from corresponding silyl enol ethers 2 and 3 occurs at the most substituted site affording ketones 8. Alkylation of corresponding lithium enolates 5 and 7 occurs at the expected site affording ketones 8 or 9. As an application the one pot synthesis of spiroketones 13 from silyl enol ethers 12 is described.
- Quesnel, Yannick,Bidois-Sery, Laure,Poirier, Jean-Marie,Duhamel, Lucette
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p. 413 - 415
(2007/10/03)
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- (E/Z) Equilibria, 16. Lone Electron Pair Donor Quality of the Imino Function: Synthesis and Reactivity of Sterically Strongly Congested Iminocyclopentanes
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2,6-Dimethyl-N-(2,2,5,5-tetramethylcyclopentylidene)aniline (4h) is obtained by permethylation; it forms salts (5) by N-protonation.Its CN double bond is strongly shielded against nucleophilic attack and cannot be hydrolyzed.Nitration and bromination occur smoothly in the aromatic p-position (12, 13), showing the directing power of the lone electron pair of the imino function.This ?-donor quality is assessed by probing weaker electrophiles and by qualitative competition experiments. Key Words: Imines / Permethylation / Substitution, electrophilic aromatic / Steric shielding
- Knorr, Rudolf,Hintermeyer-Hilpert, Monika,Mehlstaeubl, Johann,Hoang, Thi Phung,Neuner, Brigitte,Boehrer, Petra
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p. 211 - 216
(2007/10/02)
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