135286-01-0Relevant academic research and scientific papers
In Situ Conformational Fixation of the Amide Bond Enables General Access to Medium-Sized Lactams via Ring-Closing Metathesis
Hegmann, Nina,Prusko, Lea,Diesendorf, Nina,Heinrich, Markus R.
, p. 7825 - 7829 (2018)
In this work, a novel phenethylamine-derived protecting group is introduced, which is able to significantly enhance the Grubbs I-catalyzed formation of 9- to 12-membered lactams through charge-induced conformational fixation under acidic conditions. As the new approach is particularly valuable for 10- and 11-membered ring systems, for which no related precedence was available so far, the overall strategy now offers general access to medium-sized lactams via ring closing metathesis. Cleavage of the protecting group can be achieved through a mild sequence combining N-oxidation and Cope elimination or alternatively under standard hydrogenation conditions.
Thiyl radical mediated racemization of benzylic amines
Escoubet, Stephanie,Gastaldi, Stephane,Vanthuyne, Nicolas,Gil, Gerard,Siri, Didier,Bertrand, Michele P.
, p. 3242 - 3250 (2006)
Thiyl radical mediated reversible H abstraction from the stereogenic center α to the nitrogen atom is a mild method to racemize benzylic amines. Owing to the sensitivity of atomtransfer reactions to enthalpic effects, a knowledge of both the S-H and the α-C-H bond dissociation energies is fundamental to select the thiol that is appropriate to abstract the hydrogen atom from a given amine. In the absence of experimental data, theoretical calculations supply a useful predictive tool. The experiments described here are helpful in delineating the optimal conditions that have to be fulfilled for the racemization to proceed in a reasonable time in the presence of either a stoichiometric or a catalytic amount of thiol. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
Synthesis and application of Cu(II) immobilized MCM-41 based solid Lewis acid catalyst for aminolysis reaction under solvent-free condition
Chaudhary, Garima,Gupta, Neha,Singh, Amit Pratap
, (2021/07/22)
In this paper, a Cu(II) immobilized periodic mesoporous organosilica (PMOs) was synthesized and used as a reusable solid Lewis acid catalyst for the aminolysis of epoxides under solvent-free conditions. An amide-based ligand, L-propylsilyl (1) having a specific binding pocket was prepared and fabricated on mesoporous MCM-41 to produce mesoporous organosilica L-propylsilyl@MCM-41 (2). Further, it has been utilized for anchoring Cu(II) ions under controlled reaction conditions to yield solid Lewis acid catalyst Cu(II)-L-propylsilyl@MCM-41 (3). The synthesized catalyst 3 exhibits significantly higher catalytic activity for aminolysis compared to hitherto known solid Lewis acid catalysts. An extensive range of β-amino alcohols with high regio and stereoselectivity were prepared by using catalyst 3. The catalyst was recovered easily and reused eight times without any loss in its catalytic activity. Furthermore, the synthesis of clinically significant propranolol (β-blocker) from α- naphthyl glycidyl ether was attained successfully using catalyst 3 in a very decent yield.
C-H Functionalization of Amino Alcohols by Osmium Tetroxide/NMO or TPAP/NMO: Protecting Group-Free Synthesis of Indolizidines (–)-223AB and 3-epi-(–)-223AB
Chen, Wei-Lun,Wang, Lee-Ya,Li, Yu-Jang
supporting information, p. 103 - 107 (2020/01/02)
The oxidative cyclization of amino alcohols by osmium tetroxide/NMO or tetrapropylammonium perruthenate (TPAP)/NMO was found to provide an N,O-acetal moiety through the trapping of the resulting iminium ion by the alcohol. These two transformations were demonstrated in the synthesis of indolizidines (–)-223AB and 3-epi-(–)-223AB.
Green Regio- and Enantioselective Aminolysis Catalyzed by Graphite and Graphene Oxide under Solvent-Free Conditions
Acocella, Maria Rosaria,D'Urso, Luciana,Maggio, Mario,Guerra, Gaetano
, p. 1915 - 1920 (2016/07/06)
The ring-opening reactions of epoxides with amines were efficiently and regioselectively catalyzed by high-surface-area graphite and graphene oxide under metal-free and solvent-free conditions. For epoxides without aryl groups, catalytic activity was observed only for graphene oxide, and hence, the activity must have been due to its acidic groups. For styrene oxide, instead, graphite and graphene oxide exhibited rather similar catalytic activities, and hence, the activity was mainly due to activation of the electrophilic epoxide by π-stacking interactions with the graphitic π system. The described aminolysis procedure is green and cheap because the catalyst can be recovered and recycled without loss of efficiency. Moreover, these heterogeneous catalysts exert high stereoselective control in the presence of nonracemic epoxides and provide chiral β-amino alcohols with enantiomeric excess values up to 99 %.
Manganese Complexes of Pyrrole- and Indolecarboxamide Ligands: Synthesis, Structure, Electrochemistry, and Applications in Oxidative and Lewis-Acid-Assisted Catalysis
Yadav, Sunil,Kumar, Sushil,Gupta, Rajeev
, p. 5534 - 5544 (2015/12/01)
This work shows the synthesis and structural, spectroscopic, and electrochemical properties of MnIII complexes supported with pyrrole- and indolecarboxamide ligands. In all cases, the respective ligand constitutes a N4 coordination sphere about the MnIII ion. The MnIII complexes of pyrrolecarboxamide ligands are square pyramidal with a fifth Cl atom, whereas analogous complexes of indolecarboxamide ligands are essentially square planar. Electrochemical studies reveal highly negative MnIII/II and moderately positive MnIV/III redox potentials. In situ generated Mn4+ species of the pyrrolecarboxamide ligands were characterized by absorption and electron paramagnetic resonance spectroscopy. All complexes functioned as catalysts in olefin epoxidation reactions by using PhIO as the oxo-transfer agent. All complexes also acted as Lewis acid catalysts for ring-opening reactions of assorted epoxides with various nucleophiles. We also show a one-pot, two-step epoxidation reaction followed by ring opening, which illustrates the catalytic significance of the present complexes. Importantly, MnIII complexes carrying electron-donating substituents on the ligand were found to be better catalysts.
Three-dimensional {Co3+-Zn2+} and {Co 3+-Cd2+} networks originated from carboxylate-rich building blocks: Syntheses, structures, and heterogeneous catalysis
Kumar, Girijesh,Gupta, Rajeev
, p. 10773 - 10787 (2013/10/22)
The present work shows the utilization of Co3+ complexes appended with either para- or meta-arylcarboxylic acid groups as the molecular building blocks for the construction of three-dimensional {Co 3+-Zn2+} and {Co3+-Cd2+} heterobimetallic networks. The structural characterizations of these networks show several interesting features including well-defined pores and channels. These networks function as heterogeneous and reusable catalysts for the regio- and stereoselective ring-opening reactions of various epoxides and size-selective cyanation reactions of assorted aldehydes.
Aminolysis of epoxides catalyzed by three-dimensional, mesoporous titanosilicates, Ti-SBA-12 and Ti-SBA-16
Kumar, Anuj,Srinivas, Darbha
experimental part, p. 126 - 140 (2012/10/07)
The application of three-dimensional, mesoporous titanosilicates (Ti-SBA-12 and Ti-SBA-16) as reusable, solid catalysts for the synthesis of a range of β-amino alcohols in high yields and selectivity through ring-opening of epoxides with amines at ambient
Zinc tetrafluoroborate hydrate as a mild catalyst for epoxide ring opening with amines: Scope and limitations of metal tetrafluoroborates and applications in the synthesis of antihypertensive drugs (RS)/(R)/(S)-metoprolols
Pujala, Brahmam,Rana, Shivani,Chakraborti, Asit K.
experimental part, p. 8768 - 8780 (2011/12/04)
The scope and limitations of metal tetrafluoroborates have been studied for epoxide ring-opening reaction with amines, and Zn(BF4) 2?xH2O has been found to be a mild and efficient catalyst affording high yields under solvent-free conditions at rt with excellent chemo-, regio-, and stereoselectivities. The catalytic efficiency followed the order Zn(BF4)2?xH2O ? Cu(BF4)2?xH2O > Co(BF4) 2?6H2O ? Fe(BF4)2? 6H2O > LiBF4 for reactions with cyclohexene oxide and Zn(BF4)2?xH2O ? Co(BF4) 2?6H2O ? Fe(BF4)2? 6H2O > Cu(BF4)2?xH2O for stilbene oxide, but AgBF4 was ineffective. For reaction of styrene oxide with aniline, the metal tetrafluoroborates exhibited comparable regioselectivity (1:99-7:93) with preferential reaction at the benzylic carbon of the epoxide ring. A reversal of regioselectivity (91:1-69:31) in favor of the reaction at the terminal carbon of the epoxide ring was observed for reaction with morpholine. The regioselectivity was dependent on the electronic and steric factors of the epoxide and the pKa of the amine and independent of amine nucleophilicity. The role of the metal tetrafluoroborates is envisaged as "electrophile nucleophile dual activation" through cooperativity of coordination, charge-charge interaction, and hydrogen-bond formation that rationalizes the catalytic efficiency, substrate reactivity, and regioselectivity. The methodology was used for synthesis of cardiovascular drug metoprolol as racemic and enriched enantiomeric forms.
Thiourea catalyzed aminolysis of epoxides under solvent free conditions. Electronic control of regioselective ring opening
Chimni, Swapandeep Singh,Bala, Neeraj,Dixit, Vaibhav A.,Bharatam, Prasad V.
experimental part, p. 3042 - 3049 (2010/06/14)
A reactant economizing process for the regioselective aminolysis of epoxides using equimolar quantities of reactants catalyzed by the double hydrogen bond donor N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea is reported. Regioselectivity of the reaction
