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Morpholine

About: Morpholine is a research topic. Over the lifetime, 5411 publications have been published within this topic receiving 51063 citations. The topic is also known as: diethylene imidoxide & diethylene oximide.


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Journal ArticleDOI
TL;DR: Amines used as bases in copper-free, palladium-catalyzed Sonogashira reactions play a multiple role and a mechanism involving prior coordination of the alkyne is suggested, followed by deprotonation of the ligatedAlkyne by the amine.
Abstract: Amines used as bases in copper-free, palladium-catalyzed Sonogashira reactions play a multiple role. The oxidative addition of iodobenzene with [Pd 0 (PPh 3 ) 4 ] is faster when performed in the presence of amines (piperidine > morpholine). Amines also substitute one ligand L in trans-[PdI(Ph)(L) 2 ] (L=PPh 3 , AsPh 3 ) formed in the oxidative addition. This reversible reaction, which gives [PdI(Ph)L(R 2 NH)], is favored in the order AsPh 3 > PPh 3 and piperidine> morpholine. Two mechanisms are proposed for Sonogashira reactions, depending on the ligand and the amine. When L=PPh 3 , its substitution by the amine in trans-[PdI(Ph)(PPh 3 ) 3 ] is less favored than that of the alkyne. A mechanism involving prior coordination of the alkyne is suggested, followed by deprotonation of the ligated alkyne by the amine. When L=AsPh 3 , its substitution in trans-[PdI(Ph)-(AsPh 3 ) 2 ] by the piperidine is easier than that by the alkyne, leading to a different mechanism: substitution of AsPh 3 by the amine is followed by substitution of the second AsPh 3 by the alkyne to generate [PdI(Ph)(amine)-(alkyne)]. Deprotonation of the ligated alkyne by an external amine leads to the coupling product. This explains why the catalytic reactions are less efficient with AsPh 3 than with PPh 3 as ligand.

82 citations

Journal ArticleDOI
TL;DR: The second generation Hoveyda catalyst HII with amines, pyridine, and DBU (1,8-diazabicyclo[5.4]undec-7-ene) was described in this article.
Abstract: Reactions are described of the second-generation Hoveyda catalyst HII with amines, pyridine, and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), in the presence and absence of olefin substrates. These nitrogen bases have a profoundly negative impact on metathesis yields, but in most cases, they are innocuous toward the precatalyst. HII adducts were formed by primary and secondary amines (n-butylamine, sec-butylamine, benzylamine, pyrrolidine, morpholine), pyridine, and DBU at room temperature. No reaction was evident for NEt3, even at 60 °C. On longer reaction at RT, unencumbered primary amines abstract the benzylidene ligand from HII. With 10 equiv of NH2nBu, this process was complete in 12 h, affording NHnBu(CH2Ar) (Ar = o-C6H4–OiPr) and [RuCl(H2IMes)(NH2nBu)4]Cl. For benzylamine, benzylidene abstraction occurred over days at RT. No such reaction was observed for sec-butylamine, secondary amines, NEt3, pyridine, or DBU. All of these bases, however, strongly inhibited metathesis of styrene by HII, with a gener...

81 citations

Journal ArticleDOI
TL;DR: Evaluated the efficacy of 1,2,3-trisubstituted cyclopropanes as rigid replacements of beta-strand secondary structure in pseudopeptidic ligands and found that a significant number of substances inhibited renin at nanomolar concentrations.
Abstract: The 1,2,3-trisubstituted cyclopropanes 6 and 7 are the first members of a novel class of isosteric replacements for peptide linkages that are more generally represented by the dipeptide mimics 2 and 3. These unique peptide surrogates are specifically designed to lock a section of a peptide backbone in an extended beta-strand conformation (phi-angle restriction) while simultaneously enforcing one of two specifically defined orientations for the amino acid side chain (chi 1-angle restriction). Methods were first developed for the stereoselective, asymmetric synthesis of the trisubstituted cyclopropanes 15a-d, 18a-d, 22a-d, and 23a-d (Scheme II), by an efficient approach featuring the Rh2(S-MEPY)4 (11) and Rh2(R-MEPY)4 (20) catalyzed cyclization of the allylic diazoacetates 10a-d to give the optically active lactones 12a-d and 21a-d, respectively, in up to greater than or equal to 94% enantiomeric excess. Nucleophilic opening of the lactone ring of 12a-d gave the corresponding morpholine amides 14a-d. By exploiting tactics that allowed for selective epimerization of one of the two functionalized side chains on the cyclopropane nucleus, 14a-d were transformed into the two series of diastereoisomeric morpholine amide carboxylic acids 15a-d and 18a-d. Epimerization of the morpholine amide group on 14a-d followed by Jones oxidation of the intermediate alcohols gave 15a-d. Alternatively, initial oxidation of the primary alcohol groups in 14a-d followed by selective, base-catalyzed inversion alpha to the aldehyde function and then Jones oxidation gave the diastereomeric dicarboxylic acid derivatives 18a-d. In a similar fashion, the enantiomeric lactones 21a-d were converted into the two corresponding enantiomeric series of dicarboxylic acid derivatives 22a-d and 23a-d. Inhibitors of aspartic proteinases, of which renin is a typical example, are known to bind to the enzyme active site cleft in an extended conformation. Thus, in order to evaluate the efficacy of 1,2,3-trisubstituted cyclopropanes as rigid replacements of beta-strand secondary structure in pseudopeptidic ligands, 15a-d, 18a-d, 22a-d, and 23a-d were incorporated at the P3 subsite of the potential renin inhibitors 24a-h and 25a-h by coupling with the tripeptide replacement 8. A significant number of substances inhibited renin at nanomolar concentrations. On the basis of this preliminary test, 1,2,3-trisubstituted cyclopropanes do appear to constitute a viable new class of peptide mimics. Since the stereochemistry at each carbon on the cyclopropane ring may be altered, these novel replacements may also function as stereochemical probes to establish the conformation of pseudopeptide ligands bound to their macromolecular targets.

81 citations

Journal ArticleDOI
TL;DR: The theoretical calculation confirmed that morpholine is unable to function as either an electron donor or an electron acceptor to quench the BODIPY fluorescence in the neutral and basic condition via photo-induced electron transfer (PET) mechanism.
Abstract: Three uncommon morpholine-based fluorescent probes (A, B, and C) for pH were prepared by introducing morpholine residues to BODIPY dyes at 4,4′- and 2,6-positions, respectively. In contrast to morpholine-based fluorescent probes for pH reported in literature, these fluorescent probes display high fluorescence in a basic condition while they exhibit very weak fluorescence in an acidic condition. The theoretical calculation confirmed that morpholine is unable to function as either an electron donor or an electron acceptor to quench the BODIPY fluorescence in the neutral and basic condition via photoinduced electron transfer (PET) mechanism because the LUMO energy of morpholine is higher than those of the BODIPY dyes while its HOMO energy is lower than those of the BODIPY dyes. However, the protonation of tertiary amines of the morpholine residues in an acidic environment leads to fluorescence quenching of the BODIPY dyes via d-PET mechanism. The fluorescence quenching is because the protonation effectively ...

81 citations

Journal Article
TL;DR: Aminoalkohole des Typs (II) werden aus den Estern (I) nach bekannten Verfahren (→ Saurechlorid → Aldehyde → Cyanhydrine → Aminoalkhole) synthetisiert as discussed by the authors.

81 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202385
2022177
202191
2020135
2019129
2018143