941602-11-5Relevant academic research and scientific papers
Molecular Engineering of β-Substituted Oxoporphyrinogens for Hydrogen-Bond Donor Catalysis
Chahal, Mandeep K.,Payne, Daniel T.,Matsushita, Yoshitaka,Labuta, Jan,Ariga, Katsuhiko,Hill, Jonathan P.
, p. 82 - 90 (2020/01/02)
A new class of bifunctional hydrogen-bond donor organocatalyst using oxoporphyrinogens having increased intramolecular hydrogen-bond donor distances is reported. Oxoporphyrinogens are highly non-planar rigid macrocycles containing a multiple hydrogen bond-forming binding site. In this work, we describe the first example of non-planar OxPs as hydrogen-bond donor catalysts prepared using a molecular engineering approach of the binding site for dual activation of substrates. The introduction of β-substituents is key to the catalytic activity and the catalysts are able to catalyze 1,4-conjugate additions and sulfa-Michael additions, as well as, Henry and aza-Henry reactions at low catalyst loadings (≤ 1 mol-%) under mild conditions. Preliminary mechanistic studies have been carried out and a possible reaction mechanism has been proposed based on the bi-functional activation of both substrates through hydrogen-bonding interactions.
A Continuous-Flow, Two-Step, Metal-Free Process for the Synthesis of Differently Substituted Chiral 1,2-Diamino Derivatives
Pirola, Margherita,Compostella, Maria Elena,Raimondi, Laura,Puglisi, Alessandra,Benaglia, Maurizio
, p. 1430 - 1438 (2018/02/09)
The enantioselective organocatalytic reduction of aryl-substituted nitroenamines was successfully performed under continuous-flow conditions. After a preliminary screening with a 10-μL microreactor, to establish the best reaction conditions, the reduction was scaled up in a 0.5-mL mesoreactor, without appreciable loss of enantioselectivity, that remained constantly higher than 90%. The in-flow nitro reduction was also accomplished, either by Raney nickel catalyzed hydrogenation or by a metal-free methodology based on the use of the very inexpensive and readily available reducing agent trichlorosilane. The final aim is to develop a two-step, continuous-flow process for the stereoselective, metal-free, catalytic synthesis of differently functionalized chiral 1,2-diamines.
A Recyclable Hydrophobic Anchor-Tagged Asymmetric Amino Thiourea Catalyst
Jichu, Takahisa,Inokuma, Tsubasa,Aihara, Keisuke,Kohiki, Taiki,Nishida, Kodai,Shigenaga, Akira,Yamada, Ken-ichi,Otaka, Akira
, p. 3402 - 3405 (2018/08/01)
A novel, recyclable, thiourea-based asymmetric organocatalyst containing a hydrophobic anchor has been developed. The chemical nature of the hydrophobic anchor contributes to the desirable characteristics of the recyclable catalyst. The hydrophobic anchor
Iron-Catalyzed Asymmetric Nitro-Mannich Reaction
Dudek, Agata,Mlynarski, Jacek
, p. 11218 - 11224 (2017/10/27)
The first enantioselective addition of nitroalkanes to imines (nitro-Mannich reaction), mediated by an iron(II) catalyst assembled by a hindered hydroxyethyl-pybox ligand, is described. This valuable carbon-carbon bond-forming reaction proceeds smoothly at room temperature to afford enantioenriched β-nitro amines in good yields and high enantioselectivity, up to 98% with unprecedentedly low iron catalyst loading (5 mol %).
Biodegradable Chitosan-Derived Thioureas as Recoverable Supported Organocatalysts – Application to the Stereoselective Aza-Henry Reaction
Andrés, José M.,González, Fernando,Maestro, Alicia,Pedrosa, Rafael,Valle, María
, p. 3658 - 3665 (2017/07/22)
Eight different biodegradable chitosan-supported bifunctional chiral thioureas have been prepared as a greener and more sustainable alternative to those supported on petrochemical-derived polymers. These organocatalysts promoted an enantioselective aza-He
Enantioselective aza-Henry reaction of: t -Boc protected imines and nitroalkanes with bifunctional squaramide organocatalysts
Susam, Dil?ad,Tanyeli, Cihangir
, p. 3555 - 3561 (2017/07/12)
An organocatalytic asymmetric aza-Henry reaction of t-Boc protected imines with nitroalkanes has been established by chiral acid-base type bifunctional Cinchona alkaloid/squaramide organocatalysts. The cooperation of a quinine motif as a base and sterical
Organocatalytic Enantioselective Transfer Hydrogenation of β-Amino Nitroolefins
Ferraro, Antonino,Bernardi, Luca,Fochi, Mariafrancesca
supporting information, p. 1561 - 1565 (2016/10/13)
The asymmetric organocatalytic transfer hydrogenation of β-acylamino and β-tert-butyloxycarbonylamino nitroolefins has been successfully realised in excellent enantioselectivities and yields (up to >99% ee, 97% yield) with a simple thiourea catalyst and a Hantzsch ester as hydrogen source, giving a direct access to enantiomerically pure β-amino nitroalkanes. (Figure presented.).
A new family of cinchona-derived bifunctional asymmetric phase-transfer catalysts: Application to the enantio- and diastereoselective nitro-Mannich reaction of amidosulfones
Johnson, Kayli M.,Rattley, Matt S.,Sladojevich, Filippo,Barber, David M.,Nunez, Marta G.,Goldys, Anna M.,Dixon, Darren J.
supporting information; experimental part, p. 2492 - 2495 (2012/08/28)
A new family of bifunctional H-bond donor phase-transfer catalysts derived from cinchona alkaloids has been developed and evaluated in the enantio- and diastereoselective nitro-Mannich reaction of in situ generated N-Boc-protected imines of aliphatic, aromatic, and heteroaromatic aldehydes. Under optimal conditions, good reactivity and high diastereoselectivities (up to 24:1 dr) and enantioselectivities (up to 95% ee) were obtained using a 9-amino-9- deoxyepiquinidine-derived phase-transfer catalyst possessing a 3,5-bis(trifluoromethyl)phenylurea H-bond donor group at the 9-position.
The use of samarium or sodium iodide salts as an alternative for the aza-Henry reaction
Rodríguez-Solla, Humberto,Concellón, Carmen,Alvaredo, Noemí,Soengas, Raquel G.
experimental part, p. 1736 - 1744 (2012/03/10)
A novel reaction of bromonitromethane with a variety of imines in very mild conditions promoted by SmI2 and NaI to afford nitroamines or bromonitroamines is described. When these reactions were performed on sugar-based imines, the corresponding
Reversal of enantioselectivity using tethered bisguanidine catalysts in the aza-Henry reaction
Lovick, Helena M.,Michael, Forrest E.
scheme or table, p. 1016 - 1019 (2009/05/27)
A series of chiral guanidines were synthesized and shown to efficiently catalyze the aza-Henry reaction. Modifications of the catalyst structure revealed important selectivity trends as well as an intriguing reversal in stereoselectivity with bisguanidine
