作者:Evelina Colacino、Pierrick Nun、Francesco Maria Colacino、Jean Martinez、Frédéric Lamaty
DOI:10.1016/j.tet.2008.03.091
日期:2008.6
13C MAS nuclear magnetic resonance experiments. We have also studied the temperature profile during the reaction. A comparative study with the corresponding solvent-free microwave activated reaction showed the superiority of the ball-milling method; 31 examples are described, including the synthesis of the anti-aging agent C-phenyl-N-tert-butyl nitrone (PBN) and one of its analogues C-2-pyridyl-N-tert-butylnitrone
Enantioselective Addition of Ketene Silyl Acetals to Nitrones Catalyzed by Chiral Titanium Complexes. Synthesis of Optically Active <i>β</i>-Amino Acids
A chiral titanium complex, Ti(O-i-Pr)(4)/BINOL/tert-butylcatechol, catalyzesenantioselective addition reaction of ketene silyl acetals to nitrones to give optically active beta-amino acid derivatives which are biologically active compounds and useful synthetic intermediates of natural products and pharmaceuticals such as beta-lactam antibiotics. The combined process of catalytic oxidation of secondary
A Convenient Synthesis of Novel Isoxazolidine and Isoxazole Isoquinolinones Fused Hybrids
作者:Konstantinos A. Ouzounthanasis、Stergios R. Rizos、Alexandros E. Koumbis
DOI:10.3390/molecules29010091
日期:——
2-propargylbenzamide, respectively. The construction of the isoquinolinone lactam system followed by performing a selective Schmidt reaction for isoxazolidine derivatives (two steps overall), whereas the isoxazole lactams were reached via an Ullmann-type cyclisation (three steps overall). Key observations were made regarding the stereo- and regioselectivities of the reactions employed, and small libraries of
Asymmetric 1,3-Dipolar Cycloaddition Reaction of Nitrones and Acrolein with a Bis-Titanium Catalyst as Chiral Lewis Acid
作者:Taichi Kano、Takuya Hashimoto、Keiji Maruoka
DOI:10.1021/ja0523284
日期:2005.8.1
A mu-oxo-type chiral bis-Ti(IV) oxide (S,S)-1 can be successfully utilized in the asymmetric 1,3-dipolar cycloaddition reactions between various nitrones 2 and acrolein to give the corresponding isoxazolidines with high to excellent enantioselectivities. For instance, the reaction between nitrone 2 (R = t-Bu) and acrolein in the presence of 10 mol % of bis-Ti(IV) catalyst (S,S)-1 in dichloromethane at -40 degrees C gave the corresponding endo cycloadduct with 97% ee.
The triflate salts of cyclic hydrazides function as asymmetric catalysts for the [3+2] cycloadditions of nitrones with alpha,beta-unsaturated aldehydes. The camphor-derived hydrazides show a preference for the exo isomers during these reactions, providing a compliment to other organically catalyzed dipolar cycloadditions. Enantiomeric excesses as high as 93% were realized for the exo isomers, while some endo products were obtained in 94% ee. (c) 2007 Elsevier Ltd. All rights reserved.