Lactam acetals

Kostyuchenko, N. P.; Граник, В. Г.; Zhidkova, A. M.; Глушков, Р. Г.; Sheinker, Yu. N.

doi:10.1007/bf00472121

Cited by 5 publications

(6 citation statements)

References 2 publications

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“…The 1 H NMR spectra of 3d also show typical broadening of resonances with decreasing temperatures which are indicative of temperatures approaching the coalescence point (Supporting Information). A similar E/Z isomerism has been reported previously. − In the case of 3b , in addition to the 2D-NOESY, the 1D NOESY technique was used to confirm the stereochemistry and differentiate rotamers from diastereomers . Enamino ester 3b is the first example of the metal-catalyzed coupling reaction of thioamides and diazo compounds where the nitrogen atom is protected as a carbamate.…”

Section: Resultssupporting

confidence: 52%

“…(E)-Ethyl 2-(1-Methylpyrrolidin-2-ylidene)-2-phenylacetate (3a). 49 Compound 3a was synthesized using thioamide 1a and diazo compound 2a following the general procedure. Purification by flash column chromatography (10% ethyl acetate in petroleum ether to 40% ethyl acetate in petroleum ether) gave pure 3a as viscous colorless oil (45.0 mg, 0.183 mmol, 92%).…”

Section: Acs Omegamentioning

confidence: 99%

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Copper-Catalyzed Coupling of Thioamides and Donor/Acceptor-Substituted Carbenoids: Synthesis of Enamino Esters and Enaminones

Pal

Hussaini

2019

ACS Omega

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The coupling of thioamides and donor/acceptor-substituted diazocarbonyl compounds is reported for the first time. The present report provides a mild, catalytic method that couples thioamides and donor/acceptor-substituted diazocarbonyl compounds to form enamino esters and enaminones. Unlike traditional methods for the synthesis of enamino esters and enaminones from thioamides, both N-alkyl thioamides and thiocarbamates are suitable substrates in this coupling reaction. Copper(I) bromide catalyzes the reaction and provides enamino esters and enaminones chemo- and diastereoselectively in less time than Rh 2 (OAc) 4 or Ru(PPh 3 ) 3 Cl 2 catalysts.

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Section: Resultssupporting

confidence: 52%

Section: Acs Omegamentioning

confidence: 99%

Copper-Catalyzed Coupling of Thioamides and Donor/Acceptor-Substituted Carbenoids: Synthesis of Enamino Esters and Enaminones

Pal

Hussaini

2019

ACS Omega

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“…What detection techniques do chemists use? They use variable-temperature (VT) NMR, − solvent switching, − and hydrogen-bonding agents , for such a task. Hu et al showed that 1-D nuclear Overhauser effect spectroscopy (NOESY) experiments are alternatives to these methods for distinguishing between rotamers and nondouble-bonded diastereomers.…”

Section: Introductionmentioning

confidence: 99%

“…If the energy barrier between two diastereomers is >21 kJ mol –1 , then two different isomers are detectable at once, while a smaller barrier shows only the average of NMR signals from interchanging isomers . Usually, chemists use VT NMR spectroscopy to observe equilibrating diastereomers. − , Solvent switching and hydrogen-bonding agents are used less frequently for this task as these techniques require multiple experiments, making them inconvenient when the sample quantities are limited . The VT technique is useful in determining quantitative information such as the rate constant and the activation energy of such an equilibrium. , However, for general organic synthesis purposes, qualitative knowledge of diastereomers that are equilibrating at room temperature is sufficient.…”

Section: Introductionmentioning

confidence: 99%

Application of NMR Spectroscopy for the Detection of Equilibrating E–Z Diastereomers

et al. 2020

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Conjugation can lower the energy barrier for unsaturated C–C bond rotations, resulting in a mixture of equilibrating diastereomers at room temperature. Therefore, methods claiming diastereoselective synthesis of conjugated double bonds often require proof that the observed diastereomeric ratio is not because of the diastereomeric equilibration of the product. Variable-temperature (VT) NMR experiments are commonly used to distinguish between the two possibilities. However, the VT technique requires accessories for the NMR spectrometer and more setup time. Here, we show that the rarely used application of 1-D and 2-D nuclear Overhauser effect spectroscopy experiments for the detection of the equilibrating diastereomers is a convenient alternative to the VT technique.

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“…Such a change in the nature of the spectra when crossing from a less to a more polar solvent can be explained by the existence of a dynamic equilibrium between isomeric forms as a result of a prototropic tautomerism of the type C A B. The prototropic tautomerism (Scheme 2) provides the possibility of rotation relative to the exocyclic multiple bond which also leads to a dynamic Z -E isomerization [4,5]. Such an isomerization has been observed in solution for 2-carbethoxy(acetyl)methylene-4-pyrimidinones in the study [6].…”

mentioning

confidence: 97%

Studies on quinazoline chemistry. 4. Unexpected route of acylation of alkyl 2-(4,4-diphenyl-1,2,3,4-tetrahydro-2-quinazolinylidene)acetates. Molecular structure of methyl 2-(4,4-diphenyl)-1,2,3,4-tetrahydro-2-quinazolinylidene)-3-oxobutanoate

Gromachevskaya

Кайгородова

Zavodnik

et al. 2007

Chem Heterocycl Compd

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We have previously reported the reactions of o-aminophenyldiphenylcarbinol with different nitriles and perchloric acid [1,2]. Under the given reaction conditions ethyl cyanoacetate gives ethyl 2-(4,4-diphenyl-1,2,3,4-tetrahydro-2-quinazolinylidene)acetate (1b) which exists as a mixture of Z-and E-isomers [2]. It was also noted that methylation of this compound occurs via N-and C-dimethylation with migration of the exocyclic multiple bond into the heterocycle to form the corresponding ethyl 2-(3-methyl-4,4-diphenyl-3,4-dihydro-2-quinazolinyl)propanoate.In connection with such an unusual alkylation route where, in the presence of two amine nitrogen atoms, alkylation occurs at only one of these and the second alkylation is at the exocyclic multiple bond in α-position to the carboxylate group stimulated us to study the behavior of compounds 1a,b towards an acylation reaction (i.e. in conditions exchanging a "soft" electrophile (R + ) for a hard one (RC + =O)).The reaction was carried out using a twofold excess of the carboxylic acid halide at room temperature in dry benzene [3] (Scheme 1).Elemental analysis, 1 H NMR, and mass spectrometry showed that the products of monoacylation at an exocyclic C=C bond carbon atom 2a-g were obtained in the reaction (Tables 1,2, and 6).The 1 H NMR spectra of compounds 2a-g (Table 2) were recorded in different solvents and showed a marked difference in the number and position of the NH proton signals. Hence in CDCl 3 solution there were four low field signals, each of intensity 0.5H, which points to the presence in solution of two geometric Z-and _______ * For Communication 3 see [1].

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Lactam acetals

Cited by 5 publications

References 2 publications

Copper-Catalyzed Coupling of Thioamides and Donor/Acceptor-Substituted Carbenoids: Synthesis of Enamino Esters and Enaminones

Copper-Catalyzed Coupling of Thioamides and Donor/Acceptor-Substituted Carbenoids: Synthesis of Enamino Esters and Enaminones

Application of NMR Spectroscopy for the Detection of Equilibrating E–Z Diastereomers

Studies on quinazoline chemistry. 4. Unexpected route of acylation of alkyl 2-(4,4-diphenyl-1,2,3,4-tetrahydro-2-quinazolinylidene)acetates. Molecular structure of methyl 2-(4,4-diphenyl)-1,2,3,4-tetrahydro-2-quinazolinylidene)-3-oxobutanoate

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