Highly Efficient and Practical Pyrrolidine-Camphor-Derived Organocatalysts for the Direct α-Amination of Aldehydes
作者:Pang-Min Liu、Dhananjay R. Magar、Kwunmin Chen
DOI:10.1002/ejoc.201000695
日期:2010.10
for direct α-amination of aldehydes with dialkyl azodicarboxylates to give the desired α-aminated products in high chemical yields (up to 92 %) and with high to excellent levels of stereoselectivity (up to >99 % ee). The reactions proceeded rapidly (within 5 min) with low catalyst loading (5 mol-%) at ambient temperature. Enantioselective aminations of asymmetric α,α-disubstituted aldehydes in the catalytic
Asymmetric Catalysis with a Mechanically Point-Chiral Rotaxane
作者:Yusuf Cakmak、Sundus Erbas-Cakmak、David A. Leigh
DOI:10.1021/jacs.6b00303
日期:2016.2.17
Mechanical point-chirality in a [2]rotaxane is utilized for asymmetriccatalysis. Stable enantiomers of the rotaxane result from a bulky group in the middle of the thread preventing a benzylic amide macrocycle shuttling between different sides of a prochiral center, creating point chirality in the vicinity of a secondary amine group. The resulting mechanochirogenesis delivers enantioselective organocatalysis
Remarkable Reaction Rate and Excellent Enantioselective Direct α-Amination of Aldehydes with Azodicarboxylates Catalyzed by Pyrrolidinylcamphor-Derived Organocatalysts
Remarkable reaction rate and excellent enantioselective direct α-amination of unmodified aldehydes with various azodicarboxylates was catalyzed by pyrrolidinylcamphor organo-catalyst 2a (5 mol-%) to provide the desired aminated products with excellent chemical yields and high to excellent levels of enantioselectivity (up to >99%ee) at 0 °C in CH 2 Cl 2 .
Propylene carbonate is shown to be an environmentally friendly and sustainable replacement for dichloromethane and acetonitrile in proline-catalysed a-hydrazinations of aldehydes and ketones. Enantioselectivities comparable to those obtained in conventional solvents or ionic liquids can be obtained, even when using a lower catalyst loading.
A series of secondary amine–thiourea catalysts derived from l-proline and chiral diamine were prepared and successfully applied to the highly effective and enantioselectiveα-amination of unmodified aldehydes with various azodicarboxylates in excellent yields (up to 99%) and enantioselectivities (up to 99% ee) within a few minutes.