Substituent‐induced chemical shift <sup>13</sup>C NMR study of substituted 2‐phenylthiazolidines

Umarani, R.

doi:10.1002/mrc.1260301020

Cited by 2 publications

(2 citation statements)

References 8 publications

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“…The concept of the substituent sensitive polarization of the carbon-heteroatom bond is supported by the fact that the five- and six-membered rings behave analogously. One series exhibiting enough substituted derivatives for a systematic study was found in the literature (series 7) . A ρ F value of −2.6 is obtained for C-2, while ρ R is −0.7 (Table ).…”

Section: Discussionmentioning

confidence: 99%

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by¹³C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions

et al. 2001

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Substituent effects on the stabilities of the ring and chain forms in a tautomeric equilibrium of five series of 2-phenyloxazolidines or -perhydro-1,3-oxazines possessing nine different substitutions at the phenyl moiety have been studied with the aid of 13C NMR spectroscopy and PM3 charge density and energy calculations. Reaction energies of the isodesmic reactions, obtained from the calculated energies of formation, show that electron-donating substituents stabilize both the chain and ring tautomers but the effect is stronger on the stability of the chain form than on that of the ring form. The 13C chemical shift changes induced by the phenyl substituents (SCS) were analyzed by several different single and dual substituent parameter approaches. The best correlations were obtained by equation SCS = rhoFsigmaF + rhoRsigmaR. In all cases the rhoF values and in most cases also the rhoR values were negative at both the C=N and C-2 carbons, indicating a reverse behavior of the electron density. This concept could be verified by the charge density calculations. The 13C chemical shifts of the C=N and C-2 carbons show a normal dependence on the charge density (q(tot)), but the charge density shows a reverse dependence on substitution. Correlation analysis of the 13C chemical shifts, solvent effect (CDCl3 vs DMSO-d6) on the NMR behavior as well as the effect of substituents on the electron densities and on the stabilities of the ring and chain tautomers show that the substituent dependence of the relative stability of the ring and chain tautomers in equilibrium is governed by several different electronic effects. At least intramolecular hydrogen bonding between the imine nitrogen and the hydroxyl group as well as polarization of the C=N bond seem to contribute in the chain form. Stereoelectronic and electrostatic effects are possible to explain the increase in stability of the ring form by electron-donating substituents.

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Section: Discussionmentioning

confidence: 99%

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by¹³C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions

et al. 2001

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“…In spectrum of 8 the C=S resonance was replaced by signals at δ 151.5, 112.8 and 167.2 ppm, which assigned to C-4, C-5, and C-2 of a 1,3-thiazole ring, respectively. The 13 C nmr data were assigned on the basis of comparing the data obtained for 8 and 10 with those repoted in the literature for 3H-quinazolin-4-one [20] and 1,3-thiazole ring system [24]. Complete information about ir, nmr and mass spectra is presented in the experimental part.…”

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Synthesis and reactions of 3‐amino‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]‐quinazolin‐9‐one and 2‐hydrazino‐3‐phenylamino‐3H‐quinazolin‐4‐one

Saleh

Hafez

Abdel-Hay

et al. 2003

Journal of Heterocyclic Chem

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The reaction of 3-N-(2-mercapto-4-oxo-4H-quinazolin-3-yl)acetamide (1) with hydrazine hydrate yielded 3-amino-2-methyl-3H-[1,2,4]triazolo [5,1-b]quinazolin-9-one (2). The reaction of 2 with o-chlorobenzaldehyde and 2-hydroxy-naphthaldehyde gave the corresponding 3-arylidene amino derivatives 3 and 4, respectively. Condensation of 2 with 1-nitroso-2-naphthol afforded the corresponding 3-(2-hydroxy-naphthalen-1yl-diazenyl)-2-methyl-3H-[1,2,4]triazolo[5,1-b]quinazolin-9-one (5), which on subsequent reduction by SnCl 2 and HCl gave the hydrazino derivative 6. Reaction of 2 with phenyl isothiocyanate in refluxing ethanol yielded thiourea derivative 7. Ring closure of 7 subsequently cyclized on refluxing with phencyl bromide, oxalyl dichloride and chloroacetic acid afforded the corresponding thiazolidine derivatives 8, 9 and 10, respectively. Reaction of 2-mercapto-3-phenylamino-3H-quinazolin-4-one (11) with hydrazine hydrate afforded 2-hydrazino-3-phenylamino-3H-quinazolin-4-one (12). The reactivity 12 towards carbon disulphide, acetyl acetone and ethyl acetoacetate gave 13, 14 and 15, respectively. Condensation of 12 with isatin (17) was synthesized by the reaction of 12 with phthalic anhydride. All isolated products were confirmed by their ir, 1 H nmr, 13 C nmr and mass spectra. J. Heterocyclic Chem., 40, 973 (2003).Substituted 3H-quinazolin-4-ones are known to possess a wide range of pharmacological activities. Several aminoquinazolinones are found to be active on the central nervous system of mice [1] and as antitubercular agents [2]. A number of diazo, hydrazide and hydrazine derivatives are also found to be good CNS active, monoamine oxidase inhibitors [3,4] and antibacterial agents [5,6]. It was also found that some 1,2,4-triazole derivatives have been reported to possess significant antifungal, antibacterial and insecticidal properties [7-9]. Additionally, several of the thiazolidine derivatives have shown biological activity against antimicrobial [10], anticancer [11], Central Nervous System activity [12], antibacterial agents [13,14] and anti-inflammatory activity [15,16]. Thus it seemed of interest to combine the 3H-quinazolin-4-one system with triazole ring and thiazolidine ring in a single molecule as compounds of this type may possess biologically activity. Herein and in continuation of our work [17][18][19][20][21][22] we synthesized some 3H-quinazolin-4-one derivatives hoping that they may have biological interest.Compound 1 was prepared from isatoic anhydride and acetyl hydrazide followed by reaction with CS 2 in refluxing ethanol [23]. The reaction of 1 with hydrazine hydrate was heated under reflux in methanol for 3 hours to afford the new heterocylic 3-amino-2-methyl-3H-[1,2,4]triazolo[5,1-b]quinazolin-9-one (2) (Scheme 1). It was suggested that the hydrazino compound was obtained in the first step, then an internal nucleophilic attack by the NH group on the electron deficient carbonyl carbon atom took place, followed by elimination of water to give the cyclized compound 2 (Scheme 1).Compound 2 was...

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Substituent‐induced chemical shift ¹³C NMR study of substituted 2‐phenylthiazolidines

Cited by 2 publications

References 8 publications

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by¹³C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by¹³C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions

Synthesis and reactions of 3‐amino‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]‐quinazolin‐9‐one and 2‐hydrazino‐3‐phenylamino‐3H‐quinazolin‐4‐one

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Substituent‐induced chemical shift 13C NMR study of substituted 2‐phenylthiazolidines

Cited by 2 publications

References 8 publications

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by13C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by13C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions

Synthesis and reactions of 3‐amino‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]‐quinazolin‐9‐one and 2‐hydrazino‐3‐phenylamino‐3H‐quinazolin‐4‐one

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Substituent‐induced chemical shift ¹³C NMR study of substituted 2‐phenylthiazolidines

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by¹³C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions

Substituent Influences on the Stability of the Ring and Chain Tautomers in 1,3-O,N-Heterocyclic Systems: Characterization by¹³C NMR Chemical Shifts, PM3 Charge Densities, and Isodesmic Reactions