Synthesis and bifunctional asymmetric organocatalysis of helical poly(phenylacetylene)s bearing cinchona alkaloid pendants via a sulfonamide linkage
作者:Hiroki Iida、Zhenglin Tang、Eiji Yashima
DOI:10.1002/pola.26678
日期:2013.7.1
Four novel helical poly(phenylacetylene)s with amino‐functionalized cinchona alkaloid pendant groups connecting to the phenyl rings through a sulfonamide linkage were synthesized by the polymerization of the corresponding phenylacetylene monomers using Rh+(2,5‐norbornadiene)[(η6‐C6H5)B−(C6H5)3] (Rh(nbd)BPh4) as the catalyst. The optically active sulfonamide‐linked polymers adopted a helical conformation
Diaryliodonium salts as efficient Lewis acid catalysts for direct three component Mannich reactions
作者:Yanxia Zhang、Jianwei Han、Zhen-Jiang Liu
DOI:10.1039/c5ra00209e
日期:——
Diaryliodonium(iii) salts, as highly active and versatile Lewis acid catalysts for the direct three component Mannich reaction under solvent free conditions, have been investigated.
The first enantioselective Michael addition of aniline to chalcones was promoted by cheap and commercially available chincona alkaloids under solvent-free conditions. Variously substituted chalcones were examined as substrates giving the conjugate adducts in moderate to good enantioselectivity. The simple experimental procedure had no work-up and short reaction times, which are the notable advantages. (C) 2008 Elsevier Ltd. All rights reserved.
Brønsted acid catalyzed enantio- and diastereoselective one-pot three component Mannich reaction
A chiral derivative of 1,2-benzenedisulfonimide,(-)-4,5-dimethy1-3,6-bis(o-toly1)-1,2-benzenedisulfonimide is herein proven to be an efficient chiral catalyst in a one pot three-component Mannich protocol. Reaction conditions are mild and green, while the enantio- and diastereoselectivity are excellent. (C) 2015 Elsevier Ltd. All rights reserved.
Silicon-Based Lewis Acid Assisted Cinchona Alkaloid Catalysis: Highly Enantioselective Aza-Michael Reaction under Solvent-Free Conditions
The study showed that a combination of an achiral silicon-based Lewis acid and chiral Lewis base, such as iodotrimethylsilane (TMSI) and cinchonine, generated a highly enantioselective catalyst system under solvent-free conditions which gave aromatic beta-amino ketones with up to >99% ee. Mechanistic studies demonstrate the enhanced asymmetric induction may be due to the combined and competitive activation of a carbonyl moiety of chalcone with cinchonine and the silicon-based Lewis acid in the aza-Michael reaction.