1H, 13C and 15N NMR chemical shifts of substituted pyrazolo[1,5‐a]pyrimidines

¹H, ¹³C and ¹⁵N NMR chemical shifts of 10 substituted pyrazolo[1,5‐a]pyrimidines were assigned based on DQF ¹H, ¹H COSY, PFG ¹H, ¹³C HMQC and PFG ¹H,X (X = ¹³C and ¹⁵N) HMBC experiments and on literature data. Copyright © 2002 John Wiley & Sons, Ltd.     

Unequivocal total assignment of 13C and 1H NMR spectra of some pyrido[1,2‐a]pyrimidine derivatives by 2D‐NMR

We report the total assignments of the ¹³C and ¹H NMR spectra of some 4‐methyl‐2‐oxo‐(2H)‐pyrido[1,2‐a]pyrimidine and 2‐methyl‐4‐oxo‐(4H)‐pyrido[1,2‐a]pyrimidine derivatives. The products were characterized by ¹H and ¹³C NMR and reported data for similar compounds. No comparative data for the two sets of isomeric compounds with respect to ¹³C and ¹H NMR have been reported to date. We made some detailed studies of the 2D NMR spectra of these compounds and observed that assignments made for non‐protonated carbon atoms by us and those reported in the literature for similar compounds need correction. The revised assignments were made on the basis of heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) techniques. Copyright © 2003 John Wiley & Sons, Ltd.     

1H and 13C NMR spectral assignments of 2,4‐diaryl‐substituted cycloalkyl[d]pyrimidines

The proton and carbon spectra of new 2,4‐diaryl‐substituted cycloalkyl[d]pyrimidines prepared in a simple one‐pot reaction, are reported. Copyright © 2002 John Wiley & Sons, Ltd.     

Theoretical and experimental 1H, 13C and 15N NMR studies of N‐alkylation of substituted tetrazolo[1,5‐a]pyridines

The ¹⁵N as well as ¹H and ¹³C chemical shifts of nine substituted tetrazolopyridines and their corresponding tetrazolopyridinium salts have been determined by using NMR spectroscopy at the natural abundance level of all nuclei in CD₃CN. In this paper, we report, for the first time, the N‐alkylation reaction of electron deficient tetrazolopyridines. The treatment of tetrazolopyridines 5–13 with one equivalent of trialkyloxonium tetrafluoroborate leads to a mixture of two isomers, i.e. N3‐ and N2‐alkyl tetrazolo[1,5‐a]pyridinium salts. It has been observed that the N3‐isomer is always the major isomer, except in the case of the CF₃ substituent, where the two isomers are obtained in the same amount. The quaternary tetrazolopyridinium nitrogen N3 is shielded by around 100 ppm (parts per million) with respect to the parent tetrazolopyridine. Experimental data are interpreted by means of density functional theory (DFT) calculations, including solvent‐induced effects, within the conductor‐like polarizable continuum model (CPCM). Good agreements between theoretical and experimental ¹H, ¹³C and ¹⁵N NMR were found. The combination of multinuclear magnetic resonance spectroscopy with gauge including atomic orbital (GIAO) DFT calculations is a powerful tool in the structural elucidation for both neutral and cationic heterocycles and in the determination of the orientation of N‐alkylation of tetrazolopyridines. Copyright © 2009 John Wiley & Sons, Ltd.     

1H{15N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and 1H, 13C and 15N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

The ¹H{¹⁵N} NMR spectrum of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]‐pyrimidine ( 3 ) was measured by GHMQC, unambiguously assigned and compared with the spectra of 1,2,4‐triazolo[1,5‐a]pyrimidine ( 1 ) and 5,7‐dimethyl‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 2 ). A series of Au(III) chloride complexes of general formula AuLCl₃, where L = 1 , 2 , 3 , was synthesized and studied by ¹HH{¹⁵N} GHMQC and ¹H{¹³C} GHMBC. Low‐frequency shifts of 72–74 ppm (¹⁵N) and 5–6 ppm (¹³C) were observed upon complexation by Au(III) ions for the coordination site N‐3 and adjacent C‐2, C‐3a atoms, respectively. The ¹³C signals of C‐5, C‐6, C‐7 and the ¹H resonances of H‐2, H‐6 were shifted to higher frequency. Comparison with analogous Pd(II), Pt(II) and Pt(IV) complexes revealed that in the case of Au(III) coordination the ¹⁵N shifts were relatively smaller, whereas those for ¹³C and ¹H were larger. Copyright © 2002 John Wiley & Sons, Ltd.     

1H and 13C NMR assignments of four series bioactive pyrido[4,3‐d]pyrimidine derivatives

The complete ¹H and ¹³C NMR assignments of four series pyrido[4,3‐d]pyrimidine derivatives were achieved by combination of one and two‐dimensional NMR experiments, and the NMR signals of these compounds were analyzed and compared. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of Novel Disubstituted Pyrazolo[1,5‐a]pyrimidines,Imidazo[1,2‐a]pyrimidines,and Pyrimido[1,2‐a]benzimidazoles Containing Thioether and Aryl Moieties

A series of novel 6‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]‐7‐phenylpyrazolo[1,5‐a]pyrimidines, 5‐phenyl‐6‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]imidazo[1,2‐a]pyrimidines, and 2‐phenyl‐3‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]pyrimido[1,2‐a]benzimidazoles have been synthesized in four steps starting with 2‐hydroxyacetophenone. The intermediate 3‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]‐4H‐1‐benzopyran‐4‐ones reacted with pyrazol‐3‐amines, 5‐methylpyrazol‐3‐amine, and 1H‐imidazol‐2‐amine, 1H‐benzimidazol‐2‐amine via a cyclocondensation to give the title compounds in the presence of MeONa as base, respectively. The approach affords the target compounds in acceptable‐to‐good yields. The new compounds were characterized by their IR, NMR, and HR mass spectra.     

1H, 13C and 15N NMR investigation of a new,condensed hexahydro‐1,3,5‐triazine

Treatment of 2‐acetyl‐2‐methylcyclopentanone with hydrazine hydrate yielded a new condensed hexahydro‐1,3,5‐triazine (3b), which is the first example of the ketimine‐type trimers. A complete ¹H, ¹³C and ¹⁵N NMR assignment of the compound was achieved. Copyright © 2003 John Wiley & Sons, Ltd.     

1H, 13C and 15N NMR data for indolo[2,3‐b]quinolines,a novel potent anticancer drug family

The complete NMR signal assignment of title compounds were carried out by extensive use of 1D and 2D NMR techniques (1H, 13C, COSY, HSQC and HMBC). Copyright © 2013 John Wiley & Sons, Ltd.     

Heterocyclic analogs of xanthiones: 5,6‐fused 3‐methyl‐1‐phenylpyrano[2,3‐c]pyrazol‐4(1H) thiones—synthesis and NMR (1H, 13C, 15N) data

Various [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐thiones were synthesized in high yields by treatment of the corresponding [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐ones with Lawesson's reagent. Detailed NMR spectroscopic studies were undertaken of the title compounds. Complete and unambiguous assignment of chemical shifts (¹H, ¹³C, ¹⁵N) and coupling constants (¹H,¹H; ¹³C,¹H) was achieved by the combined application of various one‐ and two‐dimensional (1D and 2D) NMR spectroscopic techniques. Unequivocal mapping of most ¹³C,¹H spin coupling constants is accomplished by 2D (δ, J) long‐range INEPT spectra with selective excitation. Copyright © 2010 John Wiley & Sons, Ltd.     

1H and 13C NMR assignments of bioactive indeno[1,2‐b]indole‐10‐one derivatives

The complete ¹H and ¹³C assignments of eight bioactive indeno[1,2‐b]indole‐10‐one derivatives were accomplished by the combined use of one‐dimensional and two‐dimensional NMR experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

Pyrazolo[1,5-a]pyrimidines. A combined multinuclear magnetic resonance (1H, 13C, 15N, 19F) and DFT approach to their structural assignment

Multinuclear magnetic resonance spectroscopy together with GIAO-DFT calculations allowed establishment of the structure of the products obtained by condensation of 3(5)-amino-4-phenyl-1H-pyrazole and beta-dicarbonyl compounds bearing a trifluoromethyl group. They are 3-phenyl-5-(R)-7-trifluoromethylpyrazolo[1,5-a]pyrimidines.     

1H, 13C and 15N NMR assignments for N6‐isopentenyladenosine/inosine analogues

The complete ¹H, ¹³C and ¹⁵N NMR signals assignments of some new isopentenyladenosine analogues were achieved using one‐ and two‐dimensional experiments (gs‐NOESY, gs‐HMQC and gs‐HMBC). Copyright © 2010 John Wiley & Sons, Ltd.     

1H, 13C and 15N NMR spectral assignments for new triazapentalene derivatives

Mesomeric heteropentalene betaines are conjugated fused polyheterocyclic structures that represent interesting intermediates for organic synthesis. Five such structures, containing at least four nitrogen atoms and various substituents, have been characterized by ¹H, ¹³C and ¹⁵N NMR. We report, apparently for the first time, nitrogen NMR data and coupling information on such systems. Inter‐ring long‐range correlations across five bonds with ¹⁵N (⁵J_HN) and up to seven bonds with ¹³C (⁶J_HC and ⁷J_HC) were observed in HSQC experiments. The incorporation of an electron‐withdrawing substituent such as NO₂ was observed to cause an increase in the magnitude of the remote couplings and deshielding of nearby protons, carbons and on all nitrogen atoms of the structure, including remote ones situated on other cycles. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural and conformational analysis of 1‐oxaspiro[2.5]octane and 1‐oxa‐2‐azaspiro[2.5]octane derivatives by 1H, 13C,and 15N NMR

A structural and conformational analysis of 1‐oxaspiro[2.5]octane and 1‐oxa‐2‐azaspiro[2.5]octane derivatives was performed using ¹H, ¹³ C, and ¹⁵ N NMR spectroscopy. The relative configuration and preferred conformations were determined by analyzing the homonuclear coupling constants and chemical shifts of the protons and carbon atoms in the aliphatic rings. These parameters directly reflected the steric and electronic effects of the substituent bonded to the aliphatic six‐membered ring or to C3 or N2. The parameters also were sensitive to the anisotropic positions of these atoms in the three‐atom ring. The preferred orientation of the exocyclic substituents directed the oxidative attack. Copyright © 2012 John Wiley & Sons, Ltd.     

1H, 13C and 15N NMR spectral assignments of adenosine derivatives with different amino substituents at C6-position

The complete (1)H, (13)C and (15)N NMR signals assignment of adenosine derivatives differently substituted at C(6)-position was achieved using one- and two-dimensional experiments (gs-COSY, gs-NOESY, gs-HSQC and gs-HMBC).     

1H, 13C and 15N NMR spectra of ciprofloxacin

1H NMR assignment, including the values of delta(H) and J(H,H) for the cyclopropane moiety, and 13C NMR and 15N NMR spectral data for ciprofloxacin are presented.     

1H, 13C and 15N NMR assignments for N‐ and O‐acylethanolamines,important family of naturally occurring bioactive lipid mediators

The complete ¹H, ¹³C and ¹⁵N NMR signal assignments of some N‐ and O‐acylethanolamines, important family of naturally occurring bioactive lipid mediators, were achieved using one‐dimensional and two‐dimensional experiments (gs‐HMQC and gs‐HMBC). Copyright © 2012 John Wiley & Sons, Ltd.     

C6‐substituted purine derivatives: an experimental and theoretical 1H, 13C and 15N NMR study

We measured the ¹H, ¹³ C and ¹⁵ N chemical shifts for a series of purine derivatives bearing a norbornane substituent in position 9 and various substituents in position 6. The experimental data were complemented with density functional theory (DFT) calculations. The comparison of the calculated and experimental chemical shifts provided us with information about the tautomer and conformational equilibria of the studied compounds. Copyright © 2012 John Wiley & Sons, Ltd.     

Derivatives of pyrazinecarboxylic acid: 1H, 13C and 15N NMR spectroscopic investigations

NMR spectroscopic studies are undertaken with derivatives of 2‐pyrazinecarboxylic acid. Complete and unambiguous assignment of chemical shifts (¹H, ¹³C, ¹⁵N) and coupling constants (¹H,¹H; ¹³C,¹H; ¹⁵N,¹H) is achieved by combined application of various 1D and 2D NMR spectroscopic techniques. Unequivocal mapping of ¹³C,¹H spin coupling constants is accomplished by 2D (δ,J) long‐range INEPT spectra with selective excitation. Phenomena such as the tautomerism of 3‐hydroxy‐2‐pyrazinecarboxylic acid are discussed. Copyright © 2009 John Wiley & Sons, Ltd.