7020-93-1Relevant academic research and scientific papers
Skeletally Tunable Seven-Membered-Ring Fused Pyrroles
Andreou, Dimitrios,Essien, Nsikak B.,Pubill-Ulldemolins, Cristina,Terzidis, Michael A.,Papadopoulos, Athanasios N.,Kostakis, George E.,Lykakis, Ioannis N.
, p. 6685 - 6690 (2021/09/11)
We describe a copper-mediated method that enables the synthesis of seven-membered-ring fused pyrroles (7-mrFPs). The protocol proceeds via an in situ spiro-intermediate ring expansion and tolerates a library of 7-mrFP derivatives with a broad range of functional groups in a simple step with tangible parameters and substrate adaptations. These rare 7-mrFPs are now accessible on a millimolar scale, and selected examples exhibit high antioxidant activity.
Tunable Synthesis of α-Amino Boronic Esters from Available Aldehydes and Amines through Sequential One-Pot Dehydration and Copper-Catalyzed Borylacylation
Xia, Qi,Chang, Hua-Rong,Li, Juan,Wang, Jia-Yi,Peng, Yan-Qing,Song, Gong-Hua
, p. 2716 - 2724 (2020/01/31)
Copper-catalyzed multicomponent borylacylation of imines with acid chlorides and bis(pinacolato)diboron was developed for the preparation of synthetically useful and pharmacologically relevant α-amino boronic acid derivatives. Starting from a range of acid chlorides and imines with aryl, heteroaryl, and alkyl substituents, most of these ligand-free reactions proceeded smoothly at room temperature in moderate to good yields. Furthermore, a facile and convenient one-pot, multistep access to the direct synthesis of α-amino boronic acid derivatives from available aldehydes and amines was also developed.
Synthesis of Secondary Aldimines from the Hydrogenative Cross-Coupling of Nitriles and Amines over Al2O3-Supported Ni Catalysts
Zhou, Peng,Jiang, Liang,Wang, Shuguo,Hu, Xun,Wang, Hongming,Yuan, Ziliang,Zhang, Zehui
, p. 8413 - 8423 (2019/09/07)
A heterogeneous Ni catalyst was discovered to be active in the synthesis of secondary cross-imines via hydrogenative coupling of nitriles and amines. The mesoporous Al2O3-supported Ni nanoparticles (abbreviated as Ni/m-Al2O3-600, where 600 represents the reduction temperature) were active in hydrogenative coupling of nitriles and amines reaction at 80 °C and 1 bar H2, affording corresponding cross-imines with yields in the range 64.1-98.1%. Density functional theory calculations reveal the hydrogenation of benzonitrile (PhCN) to benzylamine (PhCH2NH2) has higher activation energy than that for hydrogenative cross-coupling of PhCN and RNH2 on the Ni/m-Al2O3-600 catalyst, suggesting the latter reaction is more favorable. The theoretical calculations are in good agreement with our experimental results.
Synthesis of organoaluminum chalcogenides and their applications in Lewis acid catalysis
Ding, Yi,Ma, Xiaoli,Liu, Yashuai,Liu, Wenqing,Ni, Congjian,Yan, Ben,Yan, Li,Yang, Zhi
, (2019/08/27)
Two chalcogenide bridged bi-aluminum compounds [LAl(NMe3)(μ-S)Al(NMe3)L] (1) and [LAl(NMe3)(μ-Se)Al(NMe3)L] (2) were synthesized by reacting LAlH(NMe3) (L = 4-methylbenzylidene-o-aminothiophenol) with
Copper-Promoted Regioselective Synthesis of Polysubstituted Pyrroles from Aldehydes, Amines, and Nitroalkenes via 1,2-Phenyl/Alkyl Migration
Andreou, Dimitrios,Kallitsakis, Michael G.,Loukopoulos, Edward,Gabriel, Catherine,Kostakis, George E.,Lykakis, Ioannis N.
supporting information, p. 2104 - 2113 (2018/02/23)
The facile copper-catalyzed synthesis of polysubstituted pyrroles from aldehydes, amines, and β-nitroalkenes is reported. Remarkably, the use of α-methyl-substituted aldehydes provides efficient access to a series of tetra- and pentasubstituted pyrroles via an overwhelming 1,2-phenyl/alkyl migration. The present methodology is also accessible to non α-substituted aldehydes, yielding the corresponding trisubstituted pyrroles. On the contrary, the use of ketones, in place of aldehydes, does not promote the organic transformation, signifying the necessity of α-substituted aldehydes. The reaction proceeds under mild catalytic conditions with low catalyst loading (0.3-1 mol %), a broad scope, very good functional-group tolerance, and high yields and can be easily scaled up to more than 3 mmol of product, thus highlighting a useful synthetic application of the present catalytic protocol. Based on formal kinetic studies, a possible radical pathway is proposed that involves the formation of an allylic nitrogen radical intermediate, which in turn reacts with the nitroalkene to yield the desired pyrrole framework via a radical 1,2-phenyl or alkyl migration.
Mechanistic Studies on the Michael Addition of Amines and Hydrazines to Nitrostyrenes: Nitroalkane Elimination via a Retro-aza-Henry-Type Process
Kallitsakis, Michael G.,Tancini, Peter D.,Dixit, Mudit,Mpourmpakis, Giannis,Lykakis, Ioannis N.
, p. 1176 - 1184 (2018/02/09)
In this article we report on the mechanistic studies of the Michael addition of amines and hydrazines to nitrostyrenes. Under the present conditions, the corresponding N-alkyl/aryl substituted benzyl imines and N-methyl/phenyl substituted benzyl hydrazones were observed via a retro-aza-Henry-type process. By combining organic synthesis and characterization experiments with computational chemistry calculations, we reveal that this reaction proceeds via a protic solvent-mediated mechanism. Experiments in deuterated methanol CD3OD reveal the synthesis and isolation of the corresponding deuterated intermediated Michael adduct, results that support the proposed slovent-mediated pathway. From the synthetic point of view, the reaction occurs under mild, noncatalytic conditions and can be used as a useful platform to yield the biologically important N-methyl pyrazoles in a one-pot manner, simple starting with the corresponding nitrostyrenes and the methylhydrazine.
Synthesis of [LAl(μ-S)2AlL] (L?=?HC(CMeNAr)2, Ar?=?2,6-Et2C6H3) with the insertion of sulfur into the Al–H bonds of LAlH2 and its application in catalysis
Zhong, Mingdong,Liu, Ying,Liu, Xin,Ma, Xiaoli,Yang, Zhi
supporting information, p. 182 - 185 (2017/05/24)
Two aluminum complexes [LAl(μ-S)2AlL] (1) and [LAl(SeH)2] (2) were synthesized in good yield by reacting one equivalent of LAlH2 (L?=?HC(CMeNAr)2, Ar?=?2,6-Et2C6H3) with one equivalent of S and with two equivalents of Se without any catalysts, respectively. Complexes 1 and 2 have been characterized by 1H and 13C NMR, elemental analyses, and single crystal X-ray structural analysis. Furthermore, the good catalytic activity of 1 as bimetallic Lewis acid catalyst for the addition reaction of TMSCN to aldehydes and aldimine condensation reactions, respectively, were investigated.
Practical Synthesis of Amides via Copper/ABNO-Catalyzed Aerobic Oxidative Coupling of Alcohols and Amines
Zultanski, Susan L.,Zhao, Jingyi,Stahl, Shannon S.
supporting information, p. 6416 - 6419 (2016/06/09)
A modular Cu/ABNO catalyst system has been identified that enables efficient aerobic oxidative coupling of alcohols and amines to amides. All four permutations of benzylic/aliphatic alcohols and primary/secondary amines are viable in this reaction, enabling broad access to secondary and tertiary amides. The reactions exhibit excellent functional group compatibility and are complete within 30 min-3 h at rt. All components of the catalyst system are commercially available.
Asymmetric induction in the addition of enantiomerically pure H-phosphinate to chiral aldimines: diastereoselective generation of α-amino phosphinates with P,C-stereogenic centers
Yang, Meng,Xu, Hao,Zhou, Zhong-Yang,Zhang, He,Liu, Li-Juan,Sun, Yong-Ming,Nie, Shao-Zhen,Zhao, Chang-Qiu
supporting information, p. 815 - 822 (2016/09/02)
α-Amino phosphinates with P,C-stereogenic centers were prepared from a P-retained addition of (RP)-(?)-menthyl H-phenylphosphinate to (R)-aldimines with up to 86:14 dr under catalyst and solvent free condition at ambient temperature; the single
Chemical reactivity and skin sensitization potential for benzaldehydes: Can Schiff base formation explain everything?
Natsch, Andreas,Gfeller, Hans,Haupt, Tina,Brunner, Gerhard
, p. 2203 - 2215 (2013/01/15)
Skin sensitizers chemically modify skin proteins rendering them immunogenic. Sensitizing chemicals have been divided into applicability domains according to their suspected reaction mechanism. The widely accepted Schiff base applicability domain covers aldehydes and ketones, and detailed structure-activity-modeling for this chemical group was presented. While Schiff base formation is the obvious reaction pathway for these chemicals, the in silico work was followed up by limited experimental work. It remains unclear whether hydrolytically labile Schiff bases can form sufficiently stable epitopes to trigger an immune response in the living organism with an excess of water being present. Here, we performed experimental studies on benzaldehydes of highly differing skin sensitization potential. Schiff base formation toward butylamine was evaluated in acetonitrile, and a detailed SAR study is presented. o-Hydroxybenzaldehydes such as salicylaldehyde and the oakmoss allergens atranol and chloratranol have a high propensity to form Schiff bases. The reactivity is highly reduced in p-hydroxy benzaldehydes such as the nonsensitizing vanillin with an intermediate reactivity for p-alkyl and p-methoxy-benzaldehydes. The work was followed up under more physiological conditions in the peptide reactivity assay with a lysine-containing heptapeptide. Under these conditions, Schiff base formation was only observable for the strong sensitizers atranol and chloratranol and for salicylaldehyde. Trapping experiments with NaBH3CN showed that Schiff base formation occurred under these conditions also for some less sensitizing aldehydes, but the reaction is not favored in the absence of in situ reduction. Surprisingly, the Schiff bases of some weaker sensitizers apparently may react further to form stable peptide adducts. These were identified as the amides between the lysine residues and the corresponding acids. Adduct formation was paralleled by oxidative deamination of the parent peptide at the lysine residue to form the peptide aldehyde. Our results explain the high sensitization potential of the oakmoss allergens by stable Schiff base formation and at the same time indicate a novel pathway for stable peptide-adduct formation and peptide modifications by aldehydes. The results thus may lead to a better understanding of the Schiff base applicability domain.
