Sweets for Catalysis - Facile Optimisation of Carbohydrate-Based Bis(oxazoline) Ligands
作者:Tobias Minuth、Mustafa Irmak、Annika Groschner、Tobias Lehnert、Mike M. K. Boysen
DOI:10.1002/ejoc.200801035
日期:2009.3
A new type of carbohydrate-basedbis(oxazoline) ligands was prepared from inexpensive D-glucosamine and tested in asymmetric cyclopropanation reactions. For optimisation, modified ligands with 3-O substituents of varying size and electronic properties were prepared as well as a 3-OH unprotected and a perpivaloylated derivative. All new ligands were tested in asymmetric cyclopropanation, revealing a
Polytopic Oxazoline-Based Chiral Ligands for Cyclopropanation Reactions: A New Strategy to Prepare Highly Recyclable Catalysts
作者:José I. García、Clara I. Herrerías、Beatriz López-Sánchez、José A. Mayoral、Oliver Reiser
DOI:10.1002/adsc.201100213
日期:2011.10
Newpolytopicchiral copper complexes based on azabis(oxazoline) moieties have been synthesized and applied in cyclopropanationreactions of several alkenes. Excellent enantioselectivities have been obtained in all cases and additionally, the catalysts have been recovered in up to 14 cycles without noticeable loss of activity and selectivity. Analysis of the copper complexes by mass spectrometry suggests
Practical Copper-Catalyzed Asymmetric Synthesis of Chiral Chrysanthemic Acid Esters
作者:Makoto Itagaki、Katsuhiro Suenobu
DOI:10.1021/op060238t
日期:2007.5.1
Practical copper salicylaldimine complex catalysts have been developed for the asymmetric synthesis of chiral chrysanthemicacid esters by the cyclopropanation reaction of 2,5-dimethyl-2,4-hexadiene with tert-butyl diazoacetate. First, the effects of the substituents on the salicylaldehyde moiety in the copper salicylaldimine complex (copper Schiff base complex) on the catalytic activity and the stereoselectivities
Catalytic Asymmetric Cyclopropanations with Nonstabilized Carbenes
作者:Kristen E. Berger、Raymond J. Martinez、Jianhan Zhou、Christopher Uyeda
DOI:10.1021/jacs.3c01949
日期:2023.5.3
general methods for the synthesis of chiral cyclopropanes are catalytic additions of diazoalkanes to alkenes. However, a limitation of this approach is that diazoalkanes can only be safely handled on preparative scales if they possess stabilizing substituents. Here we show that gem-dichloroalkanes can serve as precursors to nonstabilized carbenes for asymmetriccyclopropanation reactions of alkenes.