Zinc mediated direct transformation of propargyl N-hydroxylamines to α,β-unsaturated ketones and mechanistic insight
作者:Prasanta Das、Ashton T. Hamme
DOI:10.1016/j.tetlet.2017.01.045
日期:2017.3
A Lewis acid catalyzed direct transformation of propargyl N-hydroxylamines to α,β-unsaturated ketones in the presence of aqueous Zn(II)-salts has been described. This investigation also provides a novel observation for the stoichiometric role of Zn-halides over what is known to date for catalytic processes. A thorough mechanistic study has been established based on the experiment using 18O-labeled
synthetically useful propargyl hydroxylamines. It is noted that neither the Lewis acids (InCl3, In(OTf)3) nor the metal amides (In(HMDS)3) have activity; only the hybrids worked well, and the catalytic activity of the hybrids was shown to be much higher than that of previously reported catalysts for this reaction. The concept of a Lewis acid/metal amide hybrid as a catalyst may be expanded to broad acid/base
[GRAPHIC]Reaction of nitrones with terminal alkynes takes place readily in the presence of a substoichiometric amount of diethylzinc in toluene, affording N-propargyl-hydroxylamines in excellent yields and purity.
Reduction of 2,3-Dihydroisoxazoles to β-Amino Ketones and β-Amino Alcohols
作者:Patrick Aschwanden、Lisbet Kværnø、Roger W. Geisser、Florian Kleinbeck、Erick M. Carreira
DOI:10.1021/ol052540c
日期:2005.12.1
[chemical reaction: see text]. We report the reduction of 2,3-dihydroisoxazoles to beta-amino ketones and beta-amino alcohols. The latter are obtained in high diastereoselectivity with preference for the syn isomer.