Readily available hydrogen bond catalysts for the asymmetric transfer hydrogenation of nitroolefins
作者:Jakob F. Schneider、Markus B. Lauber、Vanessa Muhr、Domenic Kratzer、Jan Paradies
DOI:10.1039/c1ob05059a
日期:——
focuses on readily accessible thiourea hydrogen bond catalysts derived from amino acids, whose steric and electronic features are modulated by their degree of substitution at the carbinol carbon center. These catalysts were applied in the asymmetric transfer hydrogenation of nitroolefins furnishing the chiral products in up to 99% yield and 86% enantiomeric excess. The proposed catalyst's mode of action
By employing a chiral bifunctional thiourea–tertiary amine as catalyst, enantioselectiveMichaeladdition of a kojic acid derivative to nitro olefins was realised. The reactions afforded the products with good yields (up to 99%) in good enantioselectivities (up to 97% ee). In addition, the absolute configuration of one product was determined.
A Neutral, Chiral, Bis(imidazolidine)-Derived NCN-Type Palladium Pincer Complex with Catalytic Activity
作者:Takayoshi Arai、Ikiyo Oka、Takuma Morihata、Atsuko Awata、Hyuma Masu
DOI:10.1002/chem.201204017
日期:2013.1.28
Caught in a pincer: A chiral, imidazolidine‐derived NCN‐type palladiumpincercomplex has been prepared using a ligand introduction technique. Single‐crystal X‐ray diffraction analysis of this complex showed a well‐organized asymmetric sphere. The neutralpalladium/chloride version exhibited significant catalyticactivity for the reaction of nitroalkenes with malononitrile to give products in a highly
Squaramide Organocatalyzed Addition of a Masked Acyl Cyanide to β-Nitrostyrenes
作者:Alison P. Hart、Caroline J. DeGraw、Gavin J. Rustin、Matthew G. Donahue、Julie A. Pigza
DOI:10.1021/acs.joc.3c01838
日期:2023.12.1
A method for the squaramide-organocatalyzed enantioselective addition of a silyl-protected masked acyl cyanide (MAC) reagent to various β-nitrostyrenes is described. Reactions are carried out in a freezer and provide products cleanly and in high enantioselectivities at very low catalyst loadings. Adducts are then unmasked, providing various oxidation state 3 functional groups, thereby highlighting
描述了一种甲硅烷基保护的掩蔽酰基氰化物 (MAC) 试剂在方酰胺有机催化下对映选择性加成到各种 β-硝基苯乙烯上的方法。反应在冷冻机中进行,以非常低的催化剂负载量提供清洁且具有高对映选择性的产品。然后,加合物被揭开,提供各种氧化态 3 官能团,从而突出这些 MAC 试剂的实用性和制备 β-氨基酸的新策略。
First Iridium-Catalyzed Highly Enantioselective Hydrogenation of β-Nitroacrylates
The first highly chemo- and enantioselective hydrogenation of beta-nitroacrylates was accomplished with an iridium catalyst (Ir-4) with yields and enantioselectivities of up to 96% and 98% ee, respectively. The resulting alpha chiral beta-nitro propionates are attractive building blocks for the synthesis of chiral beta(2)-amino acids, which are the core scaffolds of bioactive natural products, pharmaceuticals, and beta-peptides.